Split personalities

Did you ever realize how in different situations or with different people your reactions are affected? Like how many personalities do you really possess? I know for a fact I have at least two. In school or in new situations I am completely shy and probably wouldn't talk unless someone starts the conversation and I would reply in short, quick responses. But when I'm with my friends or family I could be loud and hardly ever get embarassed, even if new people are around. Even friends that I've known for years still get shocked when I curse or do something to be center of attention. In a way I feel as if I have two sides of me.