Newbooty?
Live rock=calcium based rock that you buy that's populated by bacteria. This bacteria is part of the biological process that helps process ammonia/nitrate and nitrate in a reef tank. Sometimes you get lucky and you get some "free" corals that come in on the live rock but more often than not, you get "unlucky" and get alot of the unwanted hitchikers that come in with the live rock like pest anemones, crabs and mantis shrimp.
Reef: = usually describes a type of marine tank. There's reef, which means that the tank usually contains some fish, live rock and corals. There's fish only ("FO"), which means, literally, fish only where the tank only contains aragonite sand, fish and sometimes, dead coral skeltons for decoration. And there's and fish only with live rock ("FOWLR") which means that the tank contains only fish and live rock. No corals.
Coral = means corals. The live animals that we to keep in our aquariums in a reef type of set up.
Does that help any?
newbie: Whats the diffrence between LR, reef and coral? 
