Django auth's can do all this and more, Guardian takes advantage of this and put is all in a nice package with a good API to boot.
Have a look here on the differences django-object-permissions Vs django-guardian Vs django-authority
What does 'Object-level' permission mean?
In a wider context think of it like this. Imagine you have a profile, on that profile you can make it public, private or viewable to friends, either allowing others to view your profile or no one all.
It's the ability to limit access to specific records, rather than entire tables.