Double-hung windows are a type of window that features two movable sashes, allowing both the top and bottom sections to slide up and down. This design provides flexibility in ventilation, as you can open either the top or bottom sash, or both at the same time. These windows are commonly found in residential homes and are appreciated for their classic appearance and ease of use. They can be made from various materials, including wood, vinyl, and fiberglass, making them versatile for different architectural styles and climates.