Dormer windows are structures that extend from a sloping roof, creating additional space and light in an upper level of a building. They typically feature a vertical window set within a small roofed structure, allowing for better ventilation and natural light in attics or upper floors. These windows come in various styles, including gabled, shed, and hipped, each offering a unique aesthetic. Dormers not only enhance the appearance of a home but also increase usable space, making them a popular choice in residential architecture.