What is purpose of the Tell A Friend "Info Page Link"
The tell a friend information is stored in another table called civicrm_tell_friend. The help text for the Info Page Link says -


  A link to this Event Information page is automatically included in the email sent to friends. If you ALSO want to include a link providing general information about your organization, enter that link here (e.g http://www.example.org/) 


So basically its purpose should be to include an additional link(eg your organization) along with the message you send to the contacts from Tell a Friend form.