A PC motherboard is a printed circuit board used in laptops and personal computers. It is also known as the mainboard or planar board and occasionally abbreviated to mobo or MB. The term mainboard is also used for the main circuit board in this and other electronic devices.
A typical motherboard provides attachment points for one or more of the following: CPU, graphics card, sound card, hard disk controller, memory (RAM), and external peripheral devices. The connectors for external peripherals are nearly always color coded according to the PC 99 specification. -Wikipedia