Refresh tokens are used to generate eBay user tokens. User tokens are required for every eBay API call that returns account specific information from eBay. A user token has a life span of about two hours. To avoid forcing your user to log into eBay every time their user token expires, your application instead can store a refresh token. Refresh tokens last about 18 months. The user logs into eBay one time to associate their eBay account with your application. This gives your application permission to act on their behalf. The permission lasts for the lifetime of the refresh token or until the user revokes permission.
To generate a refresh token you need a base64 authorization code, your RuName, and an eBay user willing to give you their login credentials (It can be your account). The steps below would normally be automated