- Edited
Here's how Microsoft explains it.
https://learn.microsoft.com/en-us/windows/whats-new/ltsc/overview
I think it "updates" but only security patches. I'm not sure where it was downloaded from but I can ask my IT group.
I was able to use Windows 10 until one of the May updates installed on my computer. Even if I uninstalled the update I couldn't get it to go back to being usable because part of the update didn't seem to be able to be uninstalled. (couldn't uninstall the "Servicing Stack" that came with the update so I assume that caused the issue.)
So we started with a fresh "old" computer (Lenovo T450s) and it has been working with this LTSC version.