This document provides an overview of open textbooks and open educational resources (OER). It defines OER as teaching, learning, and research resources that reside in the public domain or are released with intellectual property licenses that allow for free use, adaptation, and distribution. The document discusses the benefits of OER including lowering costs for students and giving faculty more flexibility. It also reviews tools and repositories for finding open textbooks and a 4-step process for adopting open textbooks in courses.