Common web application tasks :-)
Seriously though - Django makes it easy to do things that you may want to do with a web application, for example:
* Handle forms for adding / updating items in a database
* Competent ORM.
* User authentication / authorization
* Simple admin interface
* Handle dynamic webbpages.
* Send dynamic email.
* Create just about anything you need to be able to create on a web application.
* Also because Django is written in python you get access to all of the Python tools and plugins.
I think the question is rather - what CAN'T you do with Django? :)
It is one of the most competent allaround frameworks I have ever seen.