Windows are openings in walls that allow light and air to enter a building. They are typically covered with glass and can be opened or closed to control ventilation. Windows come in various shapes and sizes, and they can be made from different materials, including wood, vinyl, and aluminum. In addition to providing natural light, windows also enhance the aesthetic appeal of a structure. They can be designed with different styles, such as casement, double-hung, or sliding, to suit the architectural design of a home or building. Properly installed windows can improve energy efficiency by reducing heating and cooling costs.