The Single Sign-On capability in Freshdesk lets the users arriving at your support portal login with their credentials saved on your database. 

This saves them the time and effort involved in creating a separate account for your support portal. You can also set up an SSO mechanism to validate users trying to log into your portal for Freshdesk using a locally hosted script. These could be the users who already have an account in your web application or whose information you have stored in your internal application like ActiveDirectory.