Can someone tell me what "the server app" is?

The apple article says this:

Re-enable Device Enrollment settings

1. Open the Server app. If prompted, provide your server administrator credentials.
2. Select Profile Manager in the sidebar.
3. Select the checkbox for the program that your organization uses. 

I don't know what "the server app" is. I don't see anything with 'Profile Manager' in the sidebar in Apple Business Manager or my MDM, so what the heck do they want us to do?

Also, 'Apple Business Manager' is not an option for selecting a topic in this forum.