Open Educational Resources (OERs) are teaching, learning, and research materials that are free to access and legally available for reuse, adaptation, and sharing. Examples include open textbooks, course modules, videos, assessments, and full courses.
According to David Wiley’s definition, a true OER is one that is in the public domain (free to download, use, and share) or is licensed in a manner that provides everyone with permission to engage in the 5R activities:
Understanding OER CC-BY Melody Chin, SMU Libraries