@prateek, AGP is outdated and end-of-life Graphics Port. It is lot lot slower when compared to newer PCI-Express graphics port/slot.
Only AGP cards you can find now are older cards that are still in stock with dealers. Noone is now manufacturing cards for AGP.
*en.wikipedia.org/wiki/Accelerated_Graphics_Port
AGP 8x has maximum data rate of 2133 MB/s (2 GB/s)
PCI Express 2.0 has 4 GB/s in each direction (being full duplex, it would be 8GB/s)