There are many different types of guns, one could write whole tomes on them, but the purpose of this article is to just briefly explain the most common types, this is by no means a definitive work on guns.
The two main categories of common guns are handguns and long guns. Handguns are small, designed to be held in the palm of the hand, long guns are longer and are designed to be held and braced against the shoulder.
Handguns, which are also commonly referred to as pistols, can be further broken down into two main types, revolvers and semi-automatics (some people don’t call revolvers pistols). A revolver has a rotating cylinder which holds the cartridges. Cartridges consist of a metal case which holds the primer, gun powder, and the bullet, much of the time cartridges are referred to as simply, bullets. As the hammer is cocked (pulled back), the cylinder rotates, putting the next cartridge in position to be struck by the hammer when it falls. The hammer falls due to the trigger being pulled. (On a single action revolver the hammer is pulled back with your thumb, on a double action revolver pulling the trigger will cock the hammer, rotate the cylinder, and fire the gun.)
Semi-automatics have a removable magazine (this magazine is often referred to as a clip) that holds the cartridges. On a semi-auto, when the gun is fired, the slide is thrust back expelling the spent cartridge and is pulled back via spring pushing the next cartridge from the magazine into the chamber.
Long guns can also be broken down into two main categories, shotguns and rifles. Long guns have several different methods of getting the cartridges into the chamber, so I won’t get into that. The two main differences between a shotgun and a rifle is the type of ammunition and the barrel design. A shotgun has a smooth barrel and generally shoots cartridges which contain several bullets, often referred to as shot. The shot can vary in size and number depending on the cartridge and the size of the shotgun.
Rifles are so named because their barrels interiors are not smooth. Inside of the barrel there is rifling, which are small groves that run the length of the barrel, twisting as they go (handguns also have rifled barrels). Rifle cartridges contain one bullet.