What does Report mean?
The act of sending a player to the Tribunal for judgement because he used offensive language, left the game, had a negative attitude, or broke another guideline put in the Summoner's Code.
When a player is reported, the Tribunal review the case to judge if the player should be punished. Staff at Riot Games then determine the severity of punishment. Reporting helps keep League of Legends clean and fun.
Example: Report Morde for verbal abuse and intentionally feeding after the game please.