what is a motherboard

A motherboard is the central or primary circuit board making up a complex electronic system, such as a modern computer. It is also known as a mainboard, baseboard, system board, or, on Apple computers, a logic board, and is sometimes abbreviated as mobo.The basic purpose of the motherboard, like a backplane, is to provide the electrical and logical connections by which the
othercomponents of the system communicate.

this is the other definition i added to our first wiki
the other definition is what is an expansion card which is located in another post