A window screen is a mesh barrier placed in window frames to keep insects and debris out while allowing fresh air to flow into a building. Typically made from materials like fiberglass or aluminum, these screens can be easily removed for cleaning or replacement. They come in various sizes to fit different window types. In addition to providing ventilation, window screens also help improve energy efficiency by reducing the need for air conditioning. They can be found in residential homes, commercial buildings, and even vehicles, making them a common feature in many environments where airflow is desired without unwanted pests.