Open Educational Resources (OER) are educational materials intentionally created to be free to students. These open materials are licensed by the authors/creators to permit and encourage adoption, improvement and retention. Materials may be in the form of textbooks, multimedia, full courseware, and more.
Most OER are released using terms of Creative Commons (CC) Licenses and understanding CC will help you to have a more positive experience with using OER.
Open access is a key element of Open Educational Resources. Materials accessed through a subscription, institutional membership, or paywall are not considered OER, even if they are free to the end user. Open licensing is an important aspect of the definition, as well. Materials that are openly accessible but licensed in ways which prevent modification or remixing are not considered OER, as they cannot be edited to meet varied educational needs.
Use of Open Educational Resources encourages faculty to experiment and innovate, facilitate the practice of open pedagogy, and increase affordability of and access to educational experiences.