PCI stands for Peripheral Component Interconnect. This is known to be an item that is used in order to allow personal computers to be connected with other personal computers. PCI Express is known to be a modification. AGP stands for Accelerated Graphic Port. This has been created solely to meet the needs of people who would need to have video cards.
There are a lot of people who are into online gaming right now and without the right AGP, it will be harder for video games to be played. PCI Express can also be used in order to transfer different data and other files while the AGP is meant for video games.