Dormer windows are structural extensions that project from a sloped roof, creating additional space and light in an upper level. They typically feature a vertical window set within a small roof structure, allowing for better ventilation and natural illumination in attics or lofts. These windows come in various styles, including gabled, shed, and hipped, each offering a unique aesthetic. Dormer windows not only enhance the architectural appeal of a building but also increase usable space, making them popular in residential designs, especially in homes with steeply pitched roofs.