Backseat gaming is when someone is watching you play a game telling you what to do.

This is not giving callouts or telling your teammate where you last saw the enemy. This is when you tell me how to play the entire game. "Go there" "Do this" "Go A" "Why didn't you do this".

Congratulations you just got muted

Congratulations now your teammates are throwing or trying to tk you

Congratulations your teammate disconnect

Congratulations your having a full blown argument with an ally

Congratulations you lost the match and you are now a hardstuck [insert rank here]