b.boy is the slang term for breakdancer
b boy is the word used to describe male breakdancers
and b girl
clothing is a usual indicator as to wether someone is a b boy/b girl but not always as it is a sport that people from many groups are into eg chavs punks
joining together in the love of hihop/rap associated dancing.
at times they will be subject to a minimal degree of mockin
mainly by those who wish they could dance or becouse they look different.