This game is a gun simulation wich allows you to assemble and disassemble (also know as field stripping) several firearms from different eras - the game includes assault rifles, sniper rifles, machine guns, submachine guns, pistols, revolvers and shotguns.
Assembly and dissasembly are not the only things you can do. The firearms are fully operatable, you can fire the weapons, learn how each one fires in different modes: automatic, burst (If the gun has the feature) and single fire. You can study how the guns work by deactivating some superficial features of the gun to show the mechanism and/or slowing down time to better understand the gun. You can also try to get the highest score amongst your friends.