motherboard?

The term 'Form Factor' is generally described as being Mini ATX, MicroATX or Flex. There are others & as previously correctly answered refers to the physical shape but not necessarly to the power supply. The more common board found on the entry level PC is a microATX. Recently a 'small Form Factor' size has crept in that is used by many of the low powered Atom based PCs. If your question is asked because you are replacing a board with a different make/model be aware of the need to be able to load drivers etc. on your new installation.

neiljw
September 2010

PC Tech has just recently provided an excellent answer to this question.

It said...

The form factor of a motherboard determines the specifications for its general shape and size. It also specifies what type of case and power supply will be supported, the placement of mounting holes, and the physical layout and organization of the board. Form factor is especially important if you build your own computer systems and need to ensure that you purchase the correct case and components.

Peccavi
September 2010