Counter Strike: Global Offensive (CS:GO) is the fourth iteration of the multiplayer-online-fps Counter Strike. It is the first game in the series to be playable on PC, Mac, Xbox360 and Playstation 3.
The series began in 1999 with a mod made for the game Half Life by Minh Le and Jess Cliffe. This first version of CS is known as 1.6, as this was the last official version number (before Steam began auto-updating the game, putting an end to version numbers).
Next came Counter Strike: Condition Zero and, frankly, the less said about that the better. Notably included a single-player campaign (the first and only version to do so).
Then, in 2004, Counter Strike: Source was released, running on the new Half Life 2 engine. This version included much improved graphics, with ragdoll physics and higher resolution textures. However, the now booming 1.6 competitive scene did not pick up the new game en-mass due to perceived weaknesses of the netcode and game engine.
With the current dwindling popularity of both 1.6 and Source, CS:GO has the chance to inject some mojo back into unarguably the greatest competitive game series of all time.