a handgun is a firearm designed to be handheld, in either one or both hands. this characteristic differentiates handguns as a general class of firearms from long guns such as rifles and shotguns (which usually can be braced against the shoulder).
major handgun subtypes are the revolver and pistol (including single-shot pistols, semi-automatic pistols, and machine pistols); other subtypes include derringers and pepperboxes.
the words "pistol" and "handgun" have overlapping variations, in meaning.
although handgun use often includes bracing with a second hand, the essential distinguishing characteristic of a handgun is its facility for one-handed operation.
this app contains an attachment about various types of pistol.