Okay i am new to this rooting stuff so i was wondering what is a Kernel and why do i need it for some ROMS?!? Their was something else that i read that i had to do with certain ROMS but i dont remember
Every ROM has a Kernel in it--it's required for the phone to work.
Note, the phone is a linux powered device; it's a computer. The kernel is at the operating system level, which as Kommy described is the bridge between apps and hardware.
The kernels that you see are optional mods, not mandatory ones. People flash kernels for further customization on top of a custom ROM.