Often described as electric razors with rows of tweezers instead of a cutting blade I think of these as the modern equivalent of threading as the rotary head of the epilators literally grabs the hairs as it spins over them plucking each hair out by the root.

Good for legs and arms but not underarm or bikini areas (mainly due to the sensitivity of skin in these areas), can last anything from several days to weeks. They work better on slightly thicker hairs as they are easier to grab and the hairs must be long enough for a normal tweezer to grab them. When using rotary epilators best results are achieved if the skin is pulled tight and this also avoids the incidence of pinching. Irritated skin and ingrown hairs can be a factor and can be lessened by using exfoliation and moisturizing.