Media Library

I don’t know much about all this stuff but can someone clarify the purpose of the media library dashboard? It looks like it just grabs the new items from my NAS. I can’t access my other music or videos. It looks like it tags e movies but maybe I am missing something here. What is the main purpose besides adding certain services as favorites? My last rescan added some songs twice into the media library dashboard and 3 New movies.

Do  you have your source selected for your NAS? The media library compile the data of your drives, if selected, or your NAS, and make it easy for you to search for your data.