A pool cover is a protective layer placed over a swimming pool when it is not in use. It helps keep debris, leaves, and dirt out of the water, making maintenance easier. Pool covers can also help retain heat, reducing energy costs for heating the water, and can prevent evaporation. There are different types of pool covers, including mesh covers, solid covers, and automatic covers. Mesh covers allow water to drain through while keeping larger debris out, while solid covers block all debris but may require a pump to remove rainwater. Automatic covers can be opened and closed with a motorized system for convenience.