The term OER describes any copyrighted work (excluding software, which is described by the term "open source") that is licensed in a manner that provides users with free and perpetual permission to engage in the 5 R activities:
Attribution: Lumen Learning CC-BY 4.0
Open Educational Resources (OER) are teaching, learning, and research materials in any medium - digital or otherwise - that reside in the public domain or have been released under an open license that permits no-cost access, use, adaptation, and redistribution by others with no or limited restrictions (via UNESCO).
OER are NOT just textbooks. Examples include case studies, assignments, assessment tools, software, simulations, videos, workshops, lab manuals, test banks.
Some confuse the term, "free" resources with "Open" resources.
ALL OER have a Creative Commons license.
You can learn more about Creative Commons licenses here: Licenses – Open Education College of DuPage (opencod.org)
Yes! OER are contributing to many students having equitable access to course materials on the first day of class and are supporting student retention and completion of coursework.
Take a look at this 4-minute video summarizing research findings on the effectiveness of OER course materials.