Exactly what is a mutimedia card for a digital camera?

When I first bought my camera, a Canon Powershot A530, it came with a multimedia card in it, and I can take 12 pictures at a time, and I never bought a memory card. I was wondering exactly what this, but I'm uming its some sort of a memory card. It also says MMC-16M on it, and in big font it says 16. I have no idea what this is. Could you help me? Thanks.