Universal Serial Bus. Faster than serial, can daisy chain peripheral devices to it. Used to attach all forms of peripherals, from keyboards and mice, to monitors, printers, scanners and digital cameras. Used exclusively by new Macs, and a popular item on newer PCs. Probably the interface choice of the future.
(Universal Serial Bus port) A high-speed device interface to which up to 127 peripheral devices can be daisy-chained to a single USB port. (Contrast with SCSI port.)
USB stands for Universal Serial Bus and is a technology capable of connecting a very large number of external devices on a computer. USB is intended primarily for low bandwidth (slow) components such as mice, keyboards, modems, joysticks, cameras, etc., but not fast devices like hard drives.