Gating is the nickname given to cards from Invasion block, where the card you play requires a card matching one of its colors and its type to return to the owner's hand. Cards with this disability cost less to make up for it. Many combos were created with gating creatures where cards had an ability played when they came into play.

Examples: Shivan Wurm, Natural Emergence, Marsh Crocodile

Gating returned to Magic in the Planar Chaos (set), in the form of the white "Rescue" creatures. These allowed you to return any creature you control instead.