Like its predecessors, Team Fortress 2 is focused around two opposing teams competing for an objective. These teams, Reliable Excavation & Demolition (RED) and Builders League United (BLU), are meant to represent two holding corporations that between them secretly control every government on the planet. Players can choose to play as one of nine classes in these teams, each with his own unique strengths and weaknesses. Although the abilities of a number of classes have changed from earlier Team Fortress incarnations, the basic elements of each class have remained. The game was released with six official maps, although 24 extra maps; 9 arena maps; and two training maps have been included in subsequent updates. In addition, a number of community assembled maps have been released. When players join a level for the first time, an introductory video shows how to complete its objectives. During matches, an eternally dissatisfied woman voiced by Ellen McLain announces various game events over loudspeakers. The player limit is 16 on the Xbox 360 and PlayStation 3. On the PC, a vanilla server can hold 24 players, but in 2008 Valve updated Team Fortress 2 to include a server variable that allows up to 32 players. Third party modifications have made it possible to host up to 36 players on one server.
Team Fortress 2 is the first of Valve's multiplayer games to provide detailed statistics for individual players. They include the time spent playing as each class, most points obtained and the most captures or objectives achieved in a single life. Persistent statistics tell the player how he or she is improving in relation to these statistics, such as if a player comes close to his or her record for the damage inflicted in a round. Team Fortress 2 also features numerous "achievements" for carrying out certain tasks, such as scoring a certain number of kills or completing a round within a certain time. New sets of class-specific achievements have been added in updates, which add new abilities and weapons to each class once unlocked by the player. This unlockable system has since been expanded into a random-chance system, where the player can also obtain the items simply by playing the game. Achievements unlocked and statistics from previously played games are displayed on the player's Steam Community or Xbox Live profile page.