Select this option if the PayPal account is a Sandbox account. A Sandbox account is used to test the process of payment before using the real account. You can check out this website https://developer.paypal.com.
Encrypt the payment details. In order to do this, you must have a PayPal account and you need to upload a public certificate to PayPal and get a certificate ID in return. Use the PayPal Encryption Key Manager to generate a public certificate to upload to PayPal. A form for submitting payment without encryption will look like this: