Almost all data communication between separate computers is done through serial buses or wires. Over a serial bus a computer sends bytes or other units of data one bit at a time. This is in contradistinction to parallel buses which are faster but more expensive, and which can transmit entire bytes or larger units in one time unit due to having more data wires. In fact, one of the ways of distinguishing between a computer and a network is that the former tends to use parallel buses between the components while a network uses serial buses (although some peripheral buses such as Apple's ADB are serial).