The motherboard is the main circuit board in a computer. A motherboard provides a way for the hardware in the computer to communicate with each other. It connects all the parts of a computer together.
The CPU, memory, HDD, optical drives, video cards, sound card and expansion cards all are connected to the motherboard directly or trough a transmission media(Cables)
The specification of a motherboard is known as form factor. The dimensions, PSU type, location of mounting holes, number of ports on the back panel, etc… Basically the shape and layout of the motherboard is known as form factor.

Some of the famous form factors are:

  • PC/XT
  • AT
  • Baby AT
  • ATX
  • Mini ATX
  • Micro ATX
  • Flex ATX
  • LPX
  • Mini LPX
  • NLX
  • BTX
  • Pico BTX
  • Micro BTX