Django syntax colon syntax in template tags and in reverse function

During training with Django, as an example, I discovered something I still do not know, and did not find a link to it. I'm sure it is well documented somewhere, but I did not know how to look for it. In addition, I apologize if I ask the already answered question again, I also did not find it here. What I would like to understand is the syntax "admin: ...", which I met in several contexts:

In the template .html file:

<a href="{% url admin:todo_datetime_add %}">Add Todo items</a>

In view function:

return HttpResponseRedirect(reverse("admin:todo_item_changelist"))

I looked through the djangoproject tutorial and the first 8 djangobook chapters and I did not see it there. I know, however, that a representation function can be passed in the inverse function and that the {%%} template tags "do something", but so far I have only seen the point syntax used for these cases. Maybe we use this colon to refer to administrator functions instead of dot syntax? I would really appreciate a brief explanation of what he is doing, or the link to the link would be great. And again, sorry if I ask the already answered question again.