There are a number of tiny glands in the eyelids which open through ducts onto the lid margins near the base of the eyelashes. An obstruction of the ducts of any of these glands prevents the secretions of the glands from coming out. The secretions then accumulate and the gland may get inflamed.
A stye is a small red painful boil that occurs in the eyelid at the base of an eyelash. It occurs due to an acute infection within the glands at the eyelid.
It is also called external hordeolum. Multiple styes may be present and occasionally it may involve the entire lid margin.