A musket is a long, front-loaded, over-the-shoulder gun. Muskets have been used in many wars, such as the American Civil War.
There are many types of guns. One that's gone out of style is the musket. This weapon of choice for infantrymen was distinctive in a few ways. It was fired over your shoulder (or sometimes mounted on a stand), and it had a very long barrel. It was also muzzle-loaded, which means it was loaded through the front of the gun, not the back, like most contemporary guns.