Understanding the receive tab in electrum
Those fields are encoded into the QR code, so that it is easy for the person to pay you. The payer just scans the QR code, and if their wallet knows how to read BIP21 URIs, then they will already have the amount, description, and address filled into their payment form. In addition, if the offer is only available for a limited time, the wallet will prevent/warn the user from completing the transaction.