There are many materials students and faculty can freely access online, including library resources. Only materials that have an open license or are in the public domain are OERs. This is because OERs must be open as defined by the 5R's:

From Rosario Passos. Licensed under CC By 4.0.
Accessibility
The 5 Rs of Open
- Retain: Make and own a copy
- Reuse: Use in a wide range of ways
- Revise: Adapt, modify and improve
- Remix: Combine two or more
- Redistribute: Share with others
Flyer : Open Access for Research and Open Education for Teaching, both stress the importance of making knowledge available for individuals around the world. Explains Expectations of Openness, Formats and Access Costs, etc.