Open textbooks are open educational resources (OER); they are instructional resources created and shared in ways so that more people have access to them. This is a different model than traditionally copyrighted materials. OER are defined as teaching, learning, and research resources that reside in the public domain or have been released under an intellectual property license that permits their free use and re-purposing by others (Hewlett Foundation).
Open textbooks are openly licensed using a Creative Commons license, and are offered in various e-book formats free-of-charge, or as printed books that are available at cost.
The following chapters detail the elements that go into building a textbook.