What is the difference between FIQ and IRQ interrupt system?

Chaos has already answered well, but an additional point not covered so far is that FIQ is at the end of the vector table and so it's common/traditional to just start the routine right there, whereas the IRQ vector is usually just that. (ie a jump to somewhere else). Avoiding that extra branch immediately after a full stash and context switch is a slight speed gain.

FIQs are higher priority, no doubt, remaining points i am not sure..... FIQs will support high speed data transfer (or) channel processing, where high speed data processes is required we use FIQs and generally IRQs are used normal interrupt handlling.