Open Educational Resources (OER) are an alternative to traditional commercial textbooks. OER are freely available to students digitally. So, what's the catch? Well, there isn't one really, other than to say that OER is a movement and needs your help!
OER exist for many courses and subjects, but there are still courses and subjects where no OER exist yet.
As OER become more popular across the U.S. and internationally, the more resources become available as faculty and students create them.