Team Fortress 2 is Valve's re-imagination of the classic Team Fortress game, which was released in the Orange Box in 2007. It is available through Steam's free-to-play section, as it is F2P since 2011, and is supported by in-game drops, crafting and micro transactions.
TF2 is a team-based shooter with tons of varying levels and objectives. Two teams fight for these objectives, which can be an Assault type mode, in which one team defends its points and the other pushes, or Conquest, Team Deathmatch, or more original ones such as Payload in which the two team races to get their mine-cart into the others' base before they get theirs. Players chose from nine vastly different character classes. Each of these specializes in one or two weapons and a specific role; these are Defensive, Offensive and Support.
Offensives are the Scout with fast movement and light weapons, the Soldier with medium weapons and the Pyro with flamethrower. Defensives are the Engineer who can build and repair turrets, support pads with ammo and health, the Demoman with artillery-like explosives and the Heavy who is equipped with miniguns. The Supports are Medic who heals his team, the Sniper who uses snipers over long distances, and the Spy, who is equipped with a revolver, and can become invisible or can take on the form of an enemy team member, thus confusing them.
The game has detailed statistics for every player, which can be viewed in-game. Also there is a competitive scene, with regular events with real-life prizes and money.