I am currently working on creating the license file to create a new Portal and am scratching my head over licensing. In the past we have only used AGOL and I am gathering that obfuscated a lot of the behind-the-scenes "magic" that makes it possible for individual users to access the products and functionality provided by their assigned user type.
For our Portal, we have can have 2 different user types: Viewer and GIS Professional Advanced.
At least 1 GIS Professional Advanced user is required according to the Portal licensing wizard. We mostly need Viewers, but would need some with this more highly capable user type so that's fine. For what it's worth, the GIS ProfessionalAdvanced user includes the ability to use ArcGIS Pro.
So I select the number of licenses for each user type and move forward and do not select add-ons for any other software. I'm then prompted for details for a License Manager.

When I've looked through the docs and Esri videos about setting up Portal, I've either missed or not seen anything about how the License Manager fits into all of this.
- Why do I need a license manager if I'm creating a license file in MyEsri?
- What licenses would the License Manager be managing that Portal can't?
I'm guessing it has something to do with licensing Pro for the GIS Professional Advanced users, but I'm not really sure. I need to be able to explain this to our IT team setting up all our servers why this additional piece of software needs to be installed and where. I've gotten ideas on where already, but would appreciate additional clarification on why the License Manager is necessary.