An air gun (often called pellet gun or BB gun depending on the projectile) is any variety of pneumatic weapon that propels projectiles by means of compressed air or other gas, in contrast to firearms, which use a propellant charge. Both the rifle and pistol forms (air rifle and air pistol) typically propel metallic projectiles, either pellets, or BBs. Certain types of air guns, usually rifles, may also propel arrows or darts with feathers.