Okay I'll be straight with you this is about the game genre. If you play or played a FPS game, you can literally watch any FPS game no matter how complicated t

Okay I'll be straight with you this is about the game genre. If you play or played a FPS game, you can literally watch any FPS game no matter how complicated the cast is, sooner or later you would get it. In case of Dota2 or rather any game of that genre, you need to have played any MOBA ( Multiplayer online battle arena ) game. Any Dota2 player can watch a League of Legends game, they are not the same but similar as the basic of a MOBA game are clear to that dota2 player. They just need to watch and understand the Heroes and their spells. Rest gameplay mechanics, inventory items etc are comparatively easy to follow.