A sty is a bump that forms on or in the eyelid as the result of a blocked gland. The word sty can also be spelled stye. There are two distinct types of styes: hordeolum and chalazion.Each has different causes and treatments. A hordeolum is a blockage of one of the sweat glands or oil glands found in the skin of the eyelid, while a chalazion is a blockage of a meibomian gland, which is a special oil gland unique to the eyelids. sty is a bump that forms on or in the eyelid as the result of a blocked gland. The word sty can also be spelled stye. There are two distinct types of styes: hordeolum and chalazion.