What are skylights and roof windows? Skylights and roof windows are glazed openings on a pitched or flat roof designed to provide more light to the home. As well as allowing natural light into your home, they can also allow fresh air to enter if they are openable or vented.skylight, Roof opening covered with translucent or transparent glass or plastic designed to admit daylight. Skylights have found wide application admitting steady, even light in industrial, commercial, and residential buildings, especially those with a northern orientation.