FireWire is the trade name given by Apple to a multiplexed series interface, also known as the standard IEEE 1394 and also known as the interface i.LINK, trade name used by Sony. It is a computer bus carrying both data and command signals from the various connected devices.
It can be used to connect all kinds of bandwidth-friendly devices that require stable data throughput, especially in hard drives and digital camcorders. It can power a device, as well as connect 63 devices by bus, the connection/disconnection is done while the system is running.
Up to 1,024 buses can be connected via footbridges.
The FireWire was designed at Apple Computer 1986. It became a standard in '95. As a result, other manufacturers, including Sony And Texas Instrument brought to its design.