Bounce effects return permanents from the battlefield to their owners' hands and are almost completely focused in the color blue. They're commonly used as temporary removal, to interrupt combat, protect your own cards, or force an opponent to spend mana casting the same permanent again.
One of the original bounce spells, Unsummon, returned a single creature for one blue mana while Aetherize bounces an entire attacking force. An overloaded Cyclonic Rift acts as a notable Commander trump card by returning each nonland permanent you don't control to foes’ hands.