Well that's not very nice. Gotta start somewhere. >>>>>>GD pls
Low voice: Pretty much what it sounds like, a low voice is a voice that, if female, can comfortably sing below middle c (C4), and if male, can sing below the c below that (C3).
Heavy voice: A voice with a lot of weight in its tone. Weight= depth and sound. Sometimes it sounds pushed.
Deep voice: A low voice that resonates very well with a lot of ease.
There's a bit of an overlap, but not all low voices are heavy or deep. Not all deep voices are heavy either. I hope that helps.