iTunes U is an app made by Apple that enables us to attend university without actually being there. The idea with the app is that you search out a topic that you are interested in and then download a course that has been held in that topic. You will then be assigned tasks and homework just like you would normally be in a "real" university. So the essence here is that you can attend university and many different courses for free. Simply download, watch and do your homework.
Let me show you.

When you open the app you are greeted with this screen. It is the library and it shows you all the courses that you have downloaded and you are taking part in. You will notice that the number 78 is popping up from one of the courses. This means that I have 78 assignments left in that one course.
If you press the library button you get a catologue of all the courses that are availible for you to take part in. Simply search up a topic that you are interested in and download the course - for free.
I would encourage you to take a look at iTunes U and explore all the great courses that are availible for free. Download iTunes U for free at the app store and subscribe to Latestapples via email, right there ->