CompactFlash refers to a particular form of FlashMemory. CompactFlash memory come in little (almost) square cards that are either 3.3mm (Type 1) or 5.5mm (Type 2) thick.
CompactFlash cards were invented in 1994 by !SanDisk? who still make high quality cards. They are mostly found in devices like DigitalCameras and MP3Players.
CompactFlash cards differ from other flash forms as it utilizes an in-built controller chip whereas the older SmartMedia cards don't. Due to the thicker size than other formats it also has great capacities.
Other flash formats include SmartMedia, SecureDigital (sD), xD, Sony's MemoryStick, MultiMediaCard? (MMC)