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