A French drain is a type of drainage system designed to redirect water away from specific areas, such as basements or foundations. It consists of a trench filled with gravel or rock, containing a perforated pipe that collects and channels excess water. This helps prevent flooding and water damage by allowing groundwater to flow away from structures. Typically installed around the perimeter of a building, a French drain can also be used in yards to manage surface water. Proper installation is crucial for effectiveness, ensuring that the system slopes away from the area needing protection, thus promoting efficient drainage.