What is "unlockable"

a. 1 Not capable of being locked. 2 Capable of being unlocked. n. (context video games English) An initially hidden feature that is made available to reward the player for some achievement.

Unlockable content refers to content that is available in video games but not accessible unless something is performed by the player to get access to it. Different genres of games have different styles and options of unlockable content that is standard among their games. The unlockable content varies, and can be as little as a single weapon or enhancement, to more than doubling the playable characters available to the player.