Being a "pro gamer" is based on whether or not you make substantial money from gaming...

[Seirios Kypriotakis Kormpas]

A pro gamer is anyone that games as a fulltime job. Not a sidething.if getting money from sponsors and for tournaments is your main accupation then you are a progamer. You can be the no1 player in the world it doesnt make you a progamer. If you make money of games but from youtube twitch etc then you are a professional twitch streamer or youtuber.

 

[Zachary Saul]

I.e. markiplier