Key

A key is an item which the player can use to unlock a door or container.

Just as a door doesn't have to be a literal door, a key doesn't have to be a literal key - it can be any item which changes a door's state from locked to unlocked (a keycard, a, etc.).

A key is distinct from a lockpick. A key always succeeds in unlocking the target, but a lockpick depends on a stat roll and/or the player's skill.

Common elements

 * Some games treat keys as generic and interchangeable: i.e., any key will open any lock, and a key is consumed when used. This means that keys are a commodity (often with an upper limit on the number of keys that the player can carry at one time). (This is particularly common in older games and arcade-style games, such as Gauntlet.)
 * Other games require the player to find the specific key that matches the door. (The key may or may not be removed from the player's inventory when used.) It may be possible to obtain multiple copies of the same key.
 * Some games include a (usually hard-to-obtain) skeleton key which can open any lock (sometimes with exceptions).