A turn is a unit of play in which one player (or one team) has the opportunity to act before play passes to the next. Turns impose sequencing on a game — they set who decides when, and they create the rhythm of play.
Not all games use turns. Real-time games (many video games, some party games) allow simultaneous action. Conversational games like many role-playing games use a looser model where play flows like dialogue rather than strict alternation. But turn structure is the most common way to organize player action, and the design of the turn — what you can do during it, how many actions you get, whether you can react on other players’ turns — is a fundamental mechanic.
Turn order interacts with information. In sequential turn games, later players have more information (they have seen earlier players’ choices) but may have fewer options (resources may be claimed). Managing this asymmetry is a core design problem, addressed through mechanisms like rotating first-player, draft order reversal, or compensation resources.