yeah, ALL motherboards comes with at least one, most around 3-4 PCI slots, this is where you put regular expansion cards such as lan card/modems/usb cards
an AGP doesnt come with ALL motherboards but most, its the most common type of graphics port, the top on above all the pci slots on a motherboard, for video cards only
a PCI-E (pci-express) is a new type of video card port that gives more power to the slot for better graphics performance, still new and not the common port.. AGP goes as high as 8x and PCI-E is 16x (more power)
however, you can buy a PCI video card but they are rare and not used very often, they dont perform very well because of the lack of power given to a PCI slot
understand now ??