Loft, put simply, is the “puffiness” of a jacket. It can be used when talking about both fleeces, and synthetic and natural insulation. It generally follows this rule: the more or “higher” the loft, the warmer the garment will be. Synthetic insulators have the advantage of retaining their loft better than down clothing, aiding in thermal retention. Something is needed to restore loft in down outerwear, and it is often recommended that when you dry down clothing that has been washed, you should put a couple of tennis balls in the dryer, to help the down get back to its original high-loft state.