"OER are teaching, learning, and research resources that reside in the public domain or have been released under an intellectual property license that permits their free use and re-purposing by others. Open educational resources include full courses, course materials, modules, textbooks, streaming videos, tests, software, and any other tools, materials, or techniques used to support access to knowledge." [1]
The Open Education movement is built around the 5 Rs of Open [2]
You may here the phrase "open access." OER are a subset of open access (OA). OER are always Open Access, but not all OA materials are considered OER. [3]
Virginia Course Materials Survey, 2022
"78% of all respondents expressed some level of worry about meeting their course material costs..."
It explains the “classroom revolution” of OER and hints at the possibilities available.