Coach AJ discusses a line of compression wear by Skins tested during the annual Hawaii Ironman 2008 triathlon.
This type of compression apparel is 'gradient' compression meaning that it is tighter at the extremities to help get the blood back to the heart. Lactic acid production is purportedly reduced allowing for faster recovery.
Skins, like other technical fabrics, also allows moisture-wicking for cooling and to help keep you dry.
There is also a UV (SPF) rating for this fabric as well - SPF 50+, though one would think that just the act of having any type of clothing on gives a pretty good UV resistance.
Enjoy the review!