1999 Toyota Camry Breaks

My frount right break as been grinding when I stop and this has been going on fror a few days now and just last night my uncle was driving it and he said that when he stoped he heard something pop and then he when on to tell me that he had to press on the break and that it went to the floor. I also checked on under my wheel and seen a dark brown liquid under the wheel and I looked at the breal fluid and it was some what low. What does this all mean