People learn in different ways: some read text books and follow the instructions step by step; some find videos (screencasts) helpful and some just like to dive in and play and learn from their mistakes. Increasingly, teachers try to assist their students' learning by offering them resources of various types in the hope that, with a combination of materials, one of them will hit the right button with an individual student.
I love Moodle because of the ease with which I can give my students text to read, podcasts to listen to, "how-to" movies to watch and interactive tasks to do. All these items are presented on the course page and students can go pick the one(s) they feel most comfortable with.
In my school we have classes organized according to the ability of the students. Yet on our Moodle courses, all students can see the work set for all the other classes. We use groups to make our gradebook neater but we don't use groupings to hide resources from certain...