The motherboard or mainboard is the central printed circuit board (PCB) in many modern computers and holds many of the crucial components of the system.

The motherboard or mainboard is also referred to as mainboard, system board, the mobo or, in Apple devices, the logic board.

The motherboard provides connectors for all peripherals, holds amongst other things the RAM, CPU and the BIOS.

A typical motherboard schematic from Wikipedia:

A typical motherboard schematic