The Motherboard

The motherboard is the largest and most important circuit board in the computer, also called the main board or system board.
  The CPU is located on the motherboard which does most of the processing.
The motherboard is the most complicated piece of equipment inside the computer case. This is because all of the devices connected to the computer must communicate with the CPU on the motherboard, all devices in a computer are either installed directly on the motherboard, or directly linked to it by a cable connected to a port on the motherboard, or indirectly linked to it by expansion cards.
A device which is not directly installed on the motherboard is called peripheral device. the motherboard has some ports which are on the outside of the computer case for devices to connect to it, like a keyboard and mouse, and some ports inside the case to connect devices like floppy disk drives and hard disk drives.
This figure shows the ports which are located on the outside of the computer case.

A keyboard port, a mouse port, a serial port, a parallel port, USB ports, a network port, a 1394 port and three sound ports. The serial port is called that because data is transferred serially (one bit follows the next), this port is often used for an external modem or a serial mouse (a mouse which uses a serial port). A parallel port transmits data in parallel and is used often by a printer. A universal serial bus (USB) port is used by many different input/output devices like printers, keyboards, scanners and digital cameras. A 1394 port (fire wire port) is used for high speed multimedia devices.
Components used primarily for processing:

• Central processing unit (CPU) is the computers most important chip
• Chip set which supports the CPU by controlling a lot of the motherboards activities   

Components used for temporary storage:

• Random access memory (RAM) is used to hold data and instructions as they are processed
• Cache memory to speed up memory access, depending on the type of CPU

Components which allow the CPU to communicate with other devices:

• Traces, or wires, on the motherboard used for communication
• Expansion slots to connect expansion cards to the motherboard
• The system clock which keeps communication in sync

Electrical system:

• Power supply connections to provide electricity to the motherboard and expansion cards

Programming and setup data stored on the motherboard:

• Flash ROM, a memory chip used to permanently store instructions which controls basic hardware functions
• CMOS setup chip which holds configuration data