What's the difference between open this and open that?
Open educational resources are available free online for anyone to use and also permit re-use adaptation, re-sharing, etc. The 5 Rs.
Open access resource are available free online for anyone to use as is, but they may not be revised, remixed, or redistributed. Generally OA materials are scholarly books and articles but also include government documents.
This guide includes both, as well as library resources, which are available for free to patrons of the library. These can also be used in courses.