CSGO is a gambling simulator with a lot of micro-transactions. Its like a free to play mobile game but on PC and with a price tag.
Players can get keys, chests, and virtual knives sometimes worth more than
some people's whole computers.
When players aren't scamming each other, they can usually be found
propelling on odd
geometric surfaces at high velocities.
Also there is a FPS team based multi player mini game but it is largely ignored in favor of the gambling.