"Pistol" redirects here. For other uses, see Pistol (disambiguation).
A handgun is a firearm designed to be held in the hand when used. This characteristic differentiates handguns as a general class of firearms from their larger cousins: long guns such as rifles and shotguns, mounted weapons such as machine guns and autocannons, and larger weapons such as artillery.
Some handgun subtypes include single-shot pistols, revolvers, semi-automatic pistols, and fully automatic, or machine pistols.
The overlapping variations in meaning of the words "pistol" and "handgun" are discussed below.

Multiple senses of the word "pistol"
The word "pistol" is derived from the French pistole (or pistolet), which has these possible origins:

From the Czech pistole and this one from the Czech píšťala (flute or pipe, referring to the shape of a Hussite firearm).
From the city of Pistoia, Italy, where perhaps a manufacturer was one Camillio Vettelli in the 1540s.
That early pistols were carried by cavalry in holsters hung from the pommel (or pistallo in medieval French) of a horse's saddle. Etymology of the word "pistol"
The general types of handguns are listed below in their order of historical appearance. Each type can be classified into many subtypes. Some of these types can also be differently classified using the general distinction between muzzle-loading firearms (loading from the front of the barrel) and breech-loading firearms (loading from behind the barrel).

Types of handguns
Single-shot pistols are the theoretically simplest pistols. The earliest handguns were single-shot, muzzle-loading guns with ignition provided by inserting a smoldering match cord into a touch hole. As such, they were essentially nothing more than miniature cannons, small enough to be handheld.
Improvements followed in subsequent centuries, as various types of locks (ignition devices) were invented. In the matchlock, the separate match cord was affixed to a spring-loaded pivot which could be tripped by a trigger. In the wheellock, a mechanism analogous to that used in today's cigarette lighters replaced the smoldering match cord. In the 17th century, the flintlock, which strikes a flint against steel, appeared. (The flintlock, amazingly, remained state-of-the-art for some two hundred years.) In the 19th century, percussion caps were developed, followed shortly by modern integrated-primer cartridges, and hammers therefore traded their flint for firing pins.
Single-shot pistols are not completely things of the past, as they have continued to be built (for various reasons) throughout the breech-loading era. However, for most applications, the single-shot handgun has been replaced by revolvers and semi-automatic pistols.

Single-shot pistols
Not long after the very beginning of firearms, inventors began experimenting with multi-barreled weapons in the quest for the ability to fire more than one shot before needing to reload. Not surprisingly, all types of firearms were included in their efforts, from volley guns to analogously devised handguns. Before anyone developed a practical capability for delivering multiple loads to one barrel in quick succession (which is how repeat fire is usually accomplished today), they were aggregating multiple loaded barrels into one place.
Some examples of such handguns are:

Duck's-foot pistols
Derringers
Pepper-box guns (variously referred to as pepper-box pistols or pepper-box revolvers) Revolvers
The next development in handgun history after a practical revolver was the development of the semi-automatic pistol, which uses the energy of one shot to reload the chamber for the next (typically by mechanically harnessing the energy of recoil). After a round is fired, the pistol will cycle, ejecting the spent casing and chambering a new round from the magazine, allowing another shot to take place immediately.
Some terms that have been, or still are, used as synonyms for "semi-automatic pistol" are automatic pistol, autopistol, self-loading pistol and selfloader.

Semi-automatic pistols
A machine pistol is generally defined as a firearm designed to be fired with one hand, and capable of fully automatic or selective fire. While there are a number of machine pistols such as the Glock 18 and later models of the Mauser C96, these are rare; the light weight, small size, and extremely rapid rates of fire of a machine pistol make them difficult to control, making the larger heavier submachine gun a better choice in cases where the small size of a machine pistol is not needed. Most machine pistols can attach a shoulder stock (the Heckler & Koch VP70 would only fire single rounds at a time unless the stock was attached); others, such as the Beretta 93R, add a forward handgrip. Either of these additions technically create a legal non-pistol under the US National Firearms Act, as pistols are by definition designed to be fired with one hand. The addition of a stock or forward handgrip is considered a design change that creates either a short-barreled rifle or any other weapon, and therefore such additions are generally only found on legal machine guns.

Machine pistols
Single-action (SA) handguns have a trigger whose sole function is to drop a pre-cocked hammer to discharge a cartridge. For revolvers, the popular Colt Peacemaker of Old West fame is typically thought of. Its hammer must be manually cocked for each shot. For auto-loading pistols the Colt 1911 or Browning Hi-Power are typical examples. They must be cocked for the first shot, but subsequent shots are cocked automatically. These types of guns typically have a very light and crisp trigger pull, making for more accurate target shooting.
Traditional double-action (DA) handguns have a mechanism that can be either pre-cocked, like the above single-action gun, or can be fired with the gun uncocked. In this case, the gun has an additional mechanism added to the trigger that will cock the gun (and rotate the cylinder in the case of revolvers) as the trigger is pulled. Once the trigger is pulled far enough, the hammer is released and the gun fired. For autoloading pistols the self-loading mechanism will also re-cock the hammer after the first shot is fired so that subsequent shots are fired single-action. For revolvers, each shot is fired with the hammer initially uncocked unless the shooter manually cocked the gun. Popular auto pistols in this category include the Walther P38 and Beretta Model 92. These guns typically have a longer, heavier trigger pull for the first shot then light, crisp pulls for subsequent shots. Popular revolvers include the Ruger Redhawk and Smith & Wesson Model 629. These have comparatively long, heavy trigger pulls for all shots unless the revolver is manually cocked.
Double-action only (DAO) handguns do not have the ability to be cocked and is usually evidenced by a lack of either the hammer spur or the entire hammer. A typical autopistol in this category is the Ruger KP93DAO and Taurus Millennium, and a typical revolver is the Smith & Wesson Model 642 "Centennial". All pistols in this category have a long, heavy trigger pull for all shots.
Pre-set triggers are only on autoloading pistols. In this case the pistol mechanism is always partially cocked while being carried and during firing. The partially-cocked firing pin or striker is not cocked enough to cause an accidental release to discharge a cartridge, adding to the safeness of the design, but is cocked enough to remove much of the trigger pull and weight of a purely double-action pistol. These types of pistols do not have external hammers and do not generally have a decock function. Common pistols in the category are the Springfield Armory XD and the various forms of the extremely popular Glock. The trigger pull of these guns is between double-action and single-action pistols. Pre-set triggers may or may not have a second-strike feature on a dud cartridge.
Some automatic pistol models such as the HK Heckler & Koch USP (Universal Self-loading Pistol) come in a variety of mechanism types and can be easily changed by a gunsmith for both left- and right-handed shooters and for different operating mechanism and safety features.

Operating Mechanisms
Both revolvers and semiautomatic pistols have prominent places in the world of handgun applications today. For over a century, however, a debate has continued as to which one is better for which particular application and why. Each has its place, although personal preference is as large a factor as the following variables:

reliability (likelihood of jams; how to recover from jams; how to recover from misfires)
degree of user training needed
degree and frequency of gun cleaning needed
"firepower" (usually meaning the number of rounds that can be fired before reloading; not to be confused with "stopping power")
speed and ease of reloading
bulkiness with regard to concealment Semiautomatic pistols vs. revolvers

Easier to cycle to next round in the unlikely event of a failure/blockage: all that is needed is a pull of the trigger, while in semi autos one must rack the slide, which takes the pistol out of the shooting position. See Tap Rack Bang.
Can carry more powerful rounds than most semi autos
More reliable.
Easier to aim follow up shots (lack of a recoiling slide results in less perceived recoil).
More accurate out of the box than semi autos. Advantages of revolvers

Faster firing rate and higher volume of fire.
Generally has a larger ammo capacity: A Glock 17 carries 17 rounds: while few revolvers can carry more than six.
Faster to reload: Using magazines is faster than loading individual rounds into a revolver and easier to use and more ergonomic to carry than a speedloader.
Easier to conceal in certain circumstances due to the flatter profile - there is no cylinder creating a bulge.
The mainstay cartridge of the semi-auto family, the 9mm, is widely available and inexpensive. Advantages of semiautomatics
In comparison to longer guns such as shoulder weapons (rifles and shotguns), handguns are smaller, lighter, cheaper, and easier to carry. Since firearms don't rely on the user's strength, they put weaker individuals on an equal defensive footing; when Colt produced the first practical repeating handgun, it gave rise to the saying "God created men, but Colt made them equal".

Advantages of handguns versus shoulder weapons
Handguns are often considered self-defense weapons for use under 50 meters. While a handgun in the hands of an experienced shooter may be effective at longer ranges than 50 meters, a handgun cartridge is much more limited in its energy capacity than many long gun cartridges. Many rifles are commonly able to achieve bullet velocities of over 3,000 feet per second, whereas handguns are rarely able to achieve velocities over 1,500 feet per second. Thus, long guns are generally more powerful at any range, and especially more effective at longer ranges than handguns.
A shooter is generally able to achieve considerably greater accuracy with a long gun than with a handgun. This is due partly to the longer distance between the rear and front sights, partly due to a more stable hold attainable with a long gun, and partly due to the higher muzzle velocity, which reduces the bullet travel time and thus reduces external effects on the bullet such as gravitational drop and wind.

Disadvantages of handguns versus shoulder weapons
Many handgun models are easily concealed on a person—a trait that is useful both to people wishing to bear arms for self-protection and to criminals wishing to carry a handgun for illegal purposes. For these reasons, handguns are a particular focus of debates on gun politics, and in many jurisdictions their ownership is much more heavily regulated than that of long arms.
In the United States, 48 states allow some form of concealed carry by citizens meeting training or other requirements. 39 of these states, called "shall-issue" states, require issue of a permit if there is no compelling reason not to issue a permit (such as a prior felony conviction, a restraining order, or history of mental illness). Generally, in a shall-issue state, if a person cannot obtain a concealed weapons permit once training requirements are met, that person also cannot lawfully own a firearm. The remaining 9 states, called "may-issue" states, may deny a permit for any reason, usually at the discretion of local law enforcement.
In the United States, a person must be 21 years of age to purchase a handgun or ammunition intended for a handgun from a federally licensed dealer, which is higher than the age requirement of 18 for rifles and shotguns.
In the United Kingdom, civilian ownership of almost any handgun has been outlawed since the Dunblane massacre of 1996; the only exclusion were single shot rimfire and muzzleloading pistols; all cartridge firearms were later banned in 1997. Air pistols are still legal, however, those with power levels over 6 foot pounds (half the limit for air rifles) are classified as firearms.
Civilian ownership of handguns in Australia is legal, but heavily restricted. Handguns may not be owned for self-defence purposes (Target shooting, collecting, and occupational reasons for farmers/gun dealers are, by and large, the only legal reasons for handgun ownership), and anyone wishing to possess a handgun must obtain a firearms licence and observe stringent storage regulations.
In Israel, handguns are the only type of firearms that most private citizens may own. They are licensed for self-defense purposes to eligible individuals. Current regulations limit licenses to one handgun and 50 cartridges per licensee.
See the main gun politics article or the article on concealed carry in particular for more details on this debate.

Other related info

Blowback
Concealed carry
Gun
Handgun effectiveness
Machine-pistol
Pocket pistol
Small arms
Semi-automatic pistol
Target shooting
Weapon
List of pistols