AGP stands for Accelerated Graphics Port. It was introduced by Intel around '96, I believe, as a successor to PCI dedicated specifically for graphics applications. There where a few versions that provided different bandwidth levels and higher levels of power.
It was superseded by PCIe in 2004.
It is completely worthless today. Coasterize it, shoot it, do anything with it you want except trying to jam it into a PCIe or PCI connector on your mobo.