A backplane is similar to a personal computer's motherboard and is sometimes a term improperly describing the computer's motherboard. The backplane is a printed circuit board containing connections (slots) for expansion boards and allows communication between all connected boards.
An example of a backplane used with earlier computers was the NLX (new low profile extended) form factor, which had connections for expansion cards and a motherboard. You may also find a backplane in a corporate network router, a large router that allows expansion boards and modules for enhanced communication.
There are two types of backplane systems; an active backplane and a passive backplane. An active backplane contains the slots and the necessary circuitry to manage and control all the communication between the slots. However, a passive backplane only has bus connectors and little or no additional circuitry. In a passive backplane system, all the communication is handled by one or more expansion boards connected to the backplane.