OER stands for "Open Educational Resources" and is linked to an educational movement that began 20+ years ago and has become a global educational movement. Faculty who use OER in their courses are using freely available, high-quality educational resources in order to bring textbook costs down for students.
"Open educational resources (OER) are any resources available at little or no cost that can be used for teaching, learning, or research."
The term can include textbooks, course readings, and other learning content; simulations, games, and other learning applications; syllabi, quizzes, and assessment tools; and virtually any other material that can be used for educational purposes. [...] OER can originate from colleges and universities, libraries, archival organizations, government agencies, commercial organizations such as publishers, or faculty or other individuals who develop educational resources they are willing to share."
Text source: "7 Things You Should Know About Open Educational Resources" by EDUCAUSE. Image source: "oer_logo_EN_1" by Breno Trautwein is licensed under CC BY-SA 2.0