Can anyone tell me what the difference between a pci-e video card and a agp video card?

i have got a computer with a agp 4x slot and i am wondering if a pci-e video card will go into the same slot and work|||simple answer no pci express is different to agp|||no, pci-e (pci express) is a different slot type than agp. they are different shaped slots in the motherboard. only the newer motherboards have pci-e slots. if your motherboard only has an agp slot, then you can only install an agp slot type video card.