I apologize for being obscure. Wicking fabrics are synthetic fabrics such as polypropylene or others that wick moisture off of the surface of the body. When you are cold, it makes you feel warm. When you are sweating, it lifts the sweat off your skin and allows it to evaporate off the surface of the fabric. I wear this stuff in the mountains backpacking and hunting elk. The conditions go from sweating where sweat drops off my face and runs down my glasses to sitting still in the shade, all in the same day and without changing my clothes. If I had been wearing cotton I would have been in trouble, then the moisture would stay near my skin and chill me down. Do some research on the Internet to get a more articulate and understandable explanation. The UnderArmor product is a specific kind of such wicking fabric. The polypropylene is a very old, but functional, wicking fabric.