What's the difference between a shotgun & a rifle?

A shot gun is a smooth bore gun that is intended to shoot shot (small metal balls). There could be hundreds of individual shot in a single shell. It can shoot a single slug but it is intended for shot. The pressure inside the barrel is very low and therefor the metal can be thin. A rifle has spiral groves (rifling) inside the barrel and shoots a single bullet at higher speeds and pressure. This gives the rifle a much longer range. If you shot a rifle in the air it's bullet could travel well over a mile. Therefor only shotguns should be used for aerial targets such as skeet.