They are located on the eyelid margins. The correct medical term is hordeolum.
Sties tend to be painful, especially in the early stages when swelling and redness are prominent.
With time they often form an abscess which points to the skin, more rarely toward the eyeball itself. Treatment consists of frequent hot packs, which usually speed up the formation of white heads and pointing to the surface. Antibiotic drops help to decrease the number of germs present and prevent spread. Plucking out the lash from the middle of a stye will often promote its drainage. Rarely is surgical drainage necessary.