[RyanCahoon]

Originally Posted by AndrewN

It is a 4 wire connection from computers to devices

As was stated before, it only uses two wires, a data line and a clock signal line. Other signals are sometimes passed with it, such as ground and power, but those aren't officially part of the bus specification. Compare with something like SPI (previously mentioned) that has additional signals for chip select and a second data line so it can run in full duplex (a device can send and receive at the same time)