There are three types of skylights (also called roof windows): fixed, ventilating and tubular. Each type of skylight can help brighten up your home by bringing light into the dark areas. Skylights are also used in commercial buildings. Two common types of skylights used in commercial buildings include the hip ridge skylight and the barrel vault skylight. The hip ridge skylight is a long rectangular skylight which peaks up above the roof surface to a central ridge, with a sloping triangular piece of glass on either short end. The barrel vault skylight consists of a half-sphere against an upper wall and is often seen in large arboretums (Wisegeek.com).
Fixed Skylights
Fixed skylights are skylights that do not open. They are installed for the purpose of providing additional light only. Fixed skylights are good for attics and stairwells. Fixed skylights are the most popular types of skylights.
Ventilating Skylights
Ventilating skylights are skylights that can be opened. Velux makes many different styles of ventilating skylights, including those which open electronically or manually. Ventilating skylights are the best types of skylights for kitchens or bathrooms, where they help remove excess moisture and keep a steady flow of air. Ventilating skylights can be operated by a remote control, a manual or motorized hand crank or by sensor controlled by temperature.
Tubular Skylights
Tubular skylights are the newest types of skylights on the market. Tubular skylights are small, circular shaped skylights which are typically installed in small rooms, hallways and closets. They are normally 10" or 14" in diameter. Tubular skylights can significantly decrease your energy costs by eliminating the need for electric lights during the daytime. The Velux Sun Tunnel skylight is reportedly the most reliable tubular skylight on the market. Proper installation will prevent leaking skylights.
Skylight infö curtesy network.com