A shotgun is a firearm that is usually designed to be fired from the shoulder, which uses the energy of a fixed shell to fire a number of small spherical pellets.
A view of the break-action of a typical side-by-side double-barreled shotgun, with the Anson & Deeley boxlock action open and the extractor visible. The lever and the safety catch can also be clearly seen. A double-barreled shotgun is a shotgun with two parallel barrels, allowing two shots to be fired . side to select top barrel first and the other side to select bottom barrel.
Think of the double-barreled shotguns you see on TV. In a break-action gun, the shooter pushes a switch or lever on the rifle, and the barrel.