A Motherboard (mainboard, system board, planar board or logic board) is a PCB (Printed Circuit Board) found in many modern computers which holds many of the crucial components of the system, such as the CPU (Central Processing Unit) and memory, and provides connectors for other peripherals.

Motherboard specifically refers to a PCB with expansion capability. The term mainboard is applied to devices with a single board and no additional expansions or capability. In modern terms this would include controlling boards in televisions, washing machines and other embedded systems.

Sockets for microprocessors,

Slots for main memory,

A chipset that forms an interface between the CPU's front-side bus, main memory, and peripheral buses,

Non-volatile memory chips containing firmware or BIOS,

A clock generator,

Slots for expansion cards (Via chipset)

And power connectors,