System Bus Types and Functions
The CPU moves data around the computer on pathways that interconnect it to all the other components on the motherboard. These pathways are called 'buses'.
The internal bus carries data within the motherboard.
External buses carry data to peripherals and other devices attached to the motherboard.
The lines or pins of a bus are of three types:
Address - the components pass memory addresses to one another over the address bus.
Control - used to send out signals to coordinate and manage the activities of the motherboard components.
Data - transferred between peripherals, memory and the CPU. Obviously, the data bus can be a very busy pathway.