Inside Moodle 2+, there are several roles in a hierarchy.
Admin = god (has a capability called, no kidding, "can do anything")
Manager = demi-god
Course Creator = useless role
Editing Teacher = teacher
non-editing teacher = I only do what I'm told, I can't change anything
student = student
Outside of Moodle, whatever service you're using has an administrator who controls the hardware and software supporting Moodle. That person (or people) sets up your Moodle. The fun/scarey part is that you or one of your teachers has to be god inside Moodle. While you are developing courses, I would make everybody else a manager and tell them to do nothing outside of their course ("course" is Moodlese for what I call a "classroom").
There are a number of good books about Moodle. The best place to start is with this free download Using Moodle book - MoodleDocs The next place to go is probably to look at books http://moodle.org/mod/data/view.php?id=7246 Mary Cooch's books are aimed right at teachers (she is one). She also has a YouTube channel (search for Moodlefairy).
As Moodle Admin, you should essentially go with default values until you want something you don't find in the standard setup (or, until you are annoyed by something you find in the standard setup).