You can think of the Motherboard like the body's central nervous system. Its designed to send information back and forth between all the different components which make up your computer. How quickly and effeciently it does this can be determined by many different factors.

FSB or Front Side Bus is something you will hear a lot when talking about motherboards. The FSB of a motherboard will determine just how much information can pass between the processor and the physical memory at one time. The higher the FSB the more information can pass between generally resulting in a faster processing time.

Some things the motherboard provide access to are physical memory, connections for all your devices like DVDs, CD-Roms, floppy drives, Hard Drives, mouse, keyboard and even USB connections.

Motherboards will also determine factors like what memory type can be used, how fast the memory can go, the type of processor and its speed, what kind of hard drives can be connected or even have built in audio and video for convienence.