RAID- Is hardware implemented and basically allows differen't configurations of harddrives to improve Preformence or to provide data back up. There are MANY different levels of RAID, so read up.
SATA- Is basically the new interface for Harddrives and Optical drives. The connection is hot swapable and plug and play. So Instead of using an 80 conductor, 40 pin ribbon cable, SATA uses a Serial connection thats alot smaller and faster.
Edit: I hate when people post at around the same time. ;(