In a game, a “win condition” is a set of actions that, when accomplished, lead to a victory. The phrase has a longer history in card games and role playing games, but I also think it’s an interesting concept in general because it focuses on how you achieve a victory—winning and losing can be achieved via different approaches.
Win conditions also apply more broadly to how a sports team can achieve a specific result on the season; for good teams, we can call this a “playoff condition” if you will. Last year, the Kansas City Royals went to the playoffs for the first time in a decade and were a legitimately good team.