Also called the "system board," "main board" "base board" or "logic board," it is the primary printed circuit board in a computer or other electronic device. In a modern desktop computer, the motherboard contains the CPU and memory sockets as well as the chipset, which houses the control circuits for all the peripheral devices. It also has a PCI-Express slot for a high-end display adapter and PCI slots for additional peripherals. Laptop motherboards have no expansion slots for more peripherals. See CPU, chipset, desktop board, PCI and controller.|
This earlier Baby AT style motherboard required plug-in expansion cards for almost all the peripheral devices. The ISA slots are long gone, and the AGP slot was replaced with PCI-Express.
On earlier PCs, expansion cards were required for almost all peripheral devices except keyboard and mouse. Today, enthusiasts may plug in a faster display adapter, but most peripheral control circuits are already on the motherboard.
This is the front and back of the prototype of the first IBM PC motherboard in 1981. The chips are wired together on a "breadboard." (Images courtesy of International Business Machines Corporation. Unauthorized use not permitted.)