Flash memory is a type of electrically erasable programmable read-only memory (EEPROM). Whew, that's a mouthful. The name comes from how the memory is designed -- a section of memory cells can be erased in a single action or in a "flash." A common use of flash memory is to store the BIOS settings in a computer's ROM. When the BIOS needs to be changed, the flash memory can be written in blocks, rather than bytes, making it easy to update. Most modems use flash memory for the same reason.
Though flash memory was orginally used inside computers, it has invaded many other areas outside the box. Flash memory cards used for digital cameras, cellular phones, networking hardware, and PC cards. Though the memory's read/write speed is not lightning fast, it is nice to be able to tote around a little card rather than a cumbersome hard drive.