AGP explained. They talk about AGP x 4 (133Mhz), newer cards/motherboards are now AGP x 8 (266Mhz).
Here's an image of a motherboard with an
AGP slot. The five on the left are PCI, the sixth is AGP. In this case it's green, though they're normally brown. It's the one nearest the processor slot - that's standard - and indented further in - also standard.