What is first class mail with return receipt requested?

First Class Mail with Return Receipt Requested is a postal service option offered by the United States Postal Service (USPS) that allows senders to receive confirmation when their mail has been delivered. This service combines standard first-class mail delivery with a return receipt, which can be a postcard or electronic notification signed by the recipient. It is commonly used for important documents, ensuring that the sender has proof of delivery. This option provides added security and peace of mind for both the sender and recipient.