Most websites have pages that can be accessed only if you are logged in. Certain other pages are accessible to anonymous or public visitors. If an anonymous visitor tries to access a page which needs a logged-in user, they could be routed to the login page. Ideally, after logging in, they should be routed back to the page they wished to see in the first place.
Similarly, there are pages that can only be seen by certain kinds of users. For example, Django's admin interface is only accessible to the staff. If a non-staff user tries to access the admin pages, they would be routed to the login page.
Finally, there are pages that grant access only if certain conditions are met. For example, the ability to edit a post should only ...
