Those little
pathways that channel
data and
instructions between
memory,
registers and
elements (or as jakohn said it,
multiple devices).
The word
bus is derived from the latin
omnibus with the idea that several sets of
chips can be connected to the same bus and share the same communication channels.
Three buses are usually within the
processor, the
data bus (for transferring data, duh), the
address bus (for communications between the
control unit and
memory) and the
control bus (for transmitting signals between components).