The category doesn't exist, except when you go directly to it by url.
See that button, "Create"? That's there because the category was NOT *created* (which would then change the button to "Edit"). And since there are no pages in the category, there is nothing keeping it there except that you typed in your browser the page's url (or used a link) to arrive there.
Close the page and the "category" is functionally deleted.
Categories exist whenever a page is added to it... the thing that isn't automatically created is the Category description page. To fully remove a category you need to remove the category link/reference from all pages that have it and delete the description page.
In the link given, Love Robin is correct. It's just that un-created Category description pages just don't have a default "not found" error text that shows up, unlike articles. So, it makes you think there is something there.
Why ask when it doesn't exist (see it says create lieu edit) let alone are there any pages in it!
I was explaining as well that he may've thought that it exists just because there is no 404 error, but it actually doesn't, because if it existed then it would say "Edit" instead of "Create", but since it says "Create" then IT DOESN'T EXIST!
CREATE button instead of an EDIT button. Even if there are pages "in" that uncreated Cat.
At the time the Cat is CREATED, the WikiActivity feed will record the Cat with a PLUS/NewPage icon. Just adding pages to an uncreated Cat can still happen, but the NewPage/Plus icon does not show up.
The options next to a CREATE button does not include "History". Because it has none, because it hasn't been made yet. EDIT buttons have options for History.
When an Uncreated Cat has pages added to it, it sorta exists in a type of Code-Limbo. Sorta existing while sorta not existing at the same time (Schrodinger's Category!!). Uncreated Cats "in use" can be CREATED (generating that PLUS/NewPage icon), or it can be emptied and it will cease to exist the moment you navigate away from it.
Again, the above applies to the Category description page not a category as an entity that shows up in Special:Categories which is the definitive list of categories. If a page is part of a category, the category exists (and shows up in the special page list just mentioned), but does not have a description page by default.
Example of Category description page that exists and has pages in its category: Category:Admin Forum
Example of Category description page that exists, but has content you can't see and has pages in its category: Category:Admin tools
Example of Category description page that doesn't exist and has pages in its category: Category:Alien