MMC is a type of removable flash memory card.
Like any flash memory card, it can be used to store various types of files, including photos, videos, music, or software.
MMC is smaller than Compact Flash, but larger than miniSD, TransFlash, or RS-MMC.
MMC is the same size as SD, but thinner. Most devices with SD slots can also accept MMC cards, but not vice-versa.
SD cards are generally faster than MMC, but use more power.