Team Fortress 2 is a game that is based on the classic Team Fortress or TF genre. The first game in the genre was a classic mod to Quake World (based on the first quake game). After that Valve recruited the creators of the mod and made Team Fortress Classic into Half-life. When Half-Life 2 was released the Team Fortress 2 game came with it in 2007. In 2011 Valve announced the game as Free-To-Play which opened up the game to a wider audience of eSports gamers.
The game is a first-person shooter where two teams compete in an objective game. The normal game mode is Catch The Flag (CTF) but there are exceptions like holding specific points etc. The game is normally played with 4-9 players in each team where some are playing defence and some are playing offence. To add spice to the game there are 9 different classes: Scout, Demolition Man, Soldier, HWGuy, Medic, Pyro, Sniper, Spy and Engineer. Each of these classes has different weapons. To differentiate the classes even more they have different stats when it comes to movement speed, health and armour stats as well as special abilities. The class system makes for dynamic gameplay with different strategies in terms of off/def as well as different strategies for different maps.
Team Fortress 2 have been played as an eSport since its release in 2007 but has never seemed super popular on Twitch etc. Some serious leagues like The North American league, ESEA host TF2 eSport leagues. However, recently there have been some odds up on the game at Pinnacle Sports. More bookmakers may follow.