I still don't understand what grime is

Like I know I'm sounding like old now but I know what it is but I don't know what it is (if that makes any sense..it doesn't does it lol) ok I can hear a song and be like oh ok thats a grime track, but I don't know exactly what Grime is, like what makes up grime how can you tell a songs grime is it a certain beat or the lyrics I just don't know :-(