I was trying to update .net version and packages for an old project. when I wanted to update them I see a message that say "Package Source Mapping is off." with a configure button that let me add it.

I see this https://learn.microsoft.com/en-us/nuget/consume-packages/package-source-mapping and watch the youtube video in the link but still It's completely unclear to me.

So my Question is:

What is package source mapping? (in simple term)