Threading is a method of hair removal originating in Asia. In more recent times it has gained popularity, especially with a cosmetic application (particularly for removing/shaping eyebrows).
In threading, a thin thread is doubled, then twisted. It is then rolled over areas of unwanted hair, plucking the hair at the follicle level. Unlike tweezing, where single hairs are pulled out one at a time, threading can remove short rows of hair.
Advantages cited for eyebrow threading, as opposed to eyebrow waxing, are that it provides more precise control in shaping eyebrows and is gentler on the skin.
Threading allows for a more defined and precise shape and can create better definition for eyebrows. It is also used as a method of removing unwanted hair on the entire face and upper lip area. Threading is not a good method for removing hair on arms or legs, as the hair in those regions is typically quite coarse and there is too much to remove.