Agp stands for accelerated graphics port or advanced graphics port. This is the first slot to run at 66mhz. The agp is the always the closest spot to the cpu and only works with the pentium II currently. The video card and the processor work together to bring faster processing, clearer images, blazing 3d, and agp can also utilize your ram better. It's by far the best slot on a computer if you have one.

PCI

PCI is the fastest of all the current slots. It runs on a 32 bit interface and is about 4 inches for a slot. The faster cards require a PCI slot. For example a video card or a network card.

ISA

ISA is the most basic slot, it can run at an 8 bit interface or a 16 bit interface, ISA video cards are slow. These slots are for cards that don't really need speed like a 33.6 modem or a ISDN modem. A sound card will also run on a ISA slot. The slot is about 7 inches long.

EISA

Enhanced ISA. It's not really a slot but it makes a ISA slot run at 32bit.