Can you tell me what it mean to have a type of crust on the eyelid?

Blepharitis: Eyelid margin disease is a common and chronic condition caused by inflammation of the eyelids referred to as blepharitis or meibomitis. This condition frequently occurs in people who have a tendency toward oily skin, dandruff or dry eyes. Swollen or red eyelids; burning, stinging, or itchy eyelids; blurry vision that comes and goes; scales or skin flakes at the bottom of the eyelashes; "sleep.".