text: what is "under armour"? what does it do, and...? is it good and when did people start using it? i just want to know. thanx under armour is a brand of clothing meant to be worn under uniforms. it is underwear, t shirts, socks, etc. that wick away moisture from your body and help keep your skin cool. they have a website. i have worn their t shirts that are used under bulletproof vests and they do work very well!