What's Intel Rapid Storage Technology for?

i know it has something to do with monitoring ur RAID setup (i have two 120GB intel 510 @ raid0) but is it necessary? does it improve performance?

AFAIK, it's just their marketing name for on-board RAID.
https://en.wikipedia.org/wiki/Intel_Rapid_Storage_Technology

IIRC, it does improve ICH performance compared to the "Standard" MS Intel ICH driver. I always install it on any compatible systems (older chipsets won't support RST and must use the older version 9.6 or whatever).