PCI or Peripheral Component Interconnect, peripheral means outside, allow your motherboard to expand without having to buy a new one. PCI slots can hold graphic cards, sound cards, internet hook ups and many other desirable devices. There are 4 PCI slots in that picture, the white ones, the brown PCI looking slot is actually a AGP or accelerate graphics port. There are at least 6 different PCI slots. When purchasing a device that uses a PCI port remember the PCI key (keys are notches next to the leads) layout so you can tell if it will fit. Also knowing the lead or pin count can help you in your purchase. There are specially designed 64 bit slots that 32 bit machines cannot use. PCI express is the upgraded version. They are typically smaller and more efficient. You can use devices such as risers that will add more PCI slots and different kinds to your motherboard, but you are probably better off just buying a new motherboard or computer. Normal PCI slots only run at a pitiful 33 MHz.