A Wi-Fi extender is the device used to amplify or improve Wi-Fi signal in an area. It captures the existing wireless signal, boosts its strength, and retransmits it to extend coverage, eliminating dead zones in a home or office. This device is particularly useful in larger spaces where the router's signal may be weak or obstructed. By ensuring a strong and reliable Wi-Fi connection in all areas, extenders enhance the overall internet experience and allow for better connectivity for multiple devices.