In the hgrc file for my repository, I have two paths, one default and the other upstream. They are identical.
Do I need the entry for upstream and if so why? I have no idea why I have that for upstream.
[paths]
default = https://myUrl
upstream = https://myUrl
This is just another saved remote repository.
You can name these anything you want, the "default" name is useful in that you don't have to mention where to push to or pull from, but you can name these remote repositories, "upstream" is just such a name.
If the url of "upstream" is the same as for "default" then most likely you don't need it, unless you have scripts or programs that rely on being able to issue hg pull upstream or similar.