Derringers come in numerous calibers, from 22 to 410.
PROS: Small and easy to conceal, light weight.
CONS: Limited number of cartridges that the gun will hold, usually 2, sometimes 4. After 2 - 4 shots the gun has to be reloaded.
Revolvers come in numerous calibers, lengths of barrels, and weights. Revolvers are named after the cylinder, or wheel, which holds the cartridges. It is round and rotates to the next chamber when ready to shoot.
There are single action, in which you must cock the hammer each time you want to fire and dual action, in which you just have to pull the trigger. In dual action, pulling the trigger both cocks the hammer then releases it to fire the gun.
PRO: Numerous calibers, easy to use and very few problems of jamming.
CON: Limited to 5 - 7 cartridges in the gun when fully loaded. Reloading is not as easy as with a semi-automatic handgun.
Semiautomatic handguns come in numerous calibers and sizes. There are standard, heavy weight versions with longer barrels and light weight models with shorter barrels.
Newer configurations of the semiautomatic handgun have smoother lines for concealed carry. There are fewer angles to catch on clothing if you have to draw your weapon.
Semiautomatic handguns have a magazine which holds the ammunition and feeds it into the chamber for firing. The magazine is located in the handle. The semi-auto magazines generally carry from 5 to 15 rounds, depending upon the caliber and size of the handgun. If you have extra loaded magazines, it is very easy and fast to reload. Dropping one magazine out of the handle and sliding another in place is very quick and simple.
Other features of the semi-auto include single-action or dual-action, manual safety or trigger safety, decockers, and others which can tailor a semi-automatic handgun to a person's physical abilities and preferences.