Open Textbooks have been released with an open license (usually a Creative Commons license) which allows them to be copied, shared and revised.
OER Repositories contain more than just open textbooks. They also have other digital learning materials such as:
Open Educational Resources (OER) are "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."
From The William and Flora Hewlett Foundation
OER allow users to:
Course: MAN2021 - Principles of Management / Professors: Dr. Christina Goodell and Dr. Andrea McKeon
Course: AMH2092 - African-American History and Culture (Origins to 1877) / Professor: Dr. Scott Matthews
Course: AST1002 - Intro to Astronomy Laboratory / Professor: Dr. Mike Reynolds
Course: GEB1011 - Intro to Business / Professors: Dr. Christina Goodell and Dr. Andrea McKeon
Course: AST1002 - Intro to Astronomy / Professor: Dr. Mike Reynolds
Course: ENC1101 - English Composition I / Professor: Dr. Shep Shepard
Course: ENC1102 - Writing With Texts / Professor: Dr. Dan Powell
Course: HUM2210 - Humanities: Prehistory to the 15th Century / Professor: Dr. Scott Cason
Course: MAC1105 - College Algebra / Professor: Dr. Caroline Sampson
Course: MAT1033 - Intermediate Algebra / Professor: Jerry Shawver