There could be different scenarios where client may want to view, access, or pass data to external pages from within Dynamics CRM.
External pages refer to the pages that are not part of Dynamics CRM. It can be defined as pages that you can access via an internet (with an extension like .aspx, .html, etc).
In Dynamics CRM, we always have an option to...
Continued on Source: Different Areas in Dynamics CRM Where Users Can Access External Pages | Microsoft Dynamics CRM Tips and Tricks