Open Access (OA) is a term applied to research outputs (articles, presentations, conference papers etc.) that have been made publicly available without restriction, providing another route to access academic content.
Open Educational Resources (OER) "are learning, teaching and research materials in any format and medium that reside in the public domain or are under copyright that have been released under an open license, that permit no-cost access, re-use, re-purpose, adaptation and redistribution by others." (UNESCO, 2025)
In practice, they can be books, journals, websites, courses, videos, blogs, podcasts or anything that instructs students and is freely available for sharing.
OERs also have the advantage of being completely free to use and re-use, as long as due credit is given in the references.
Please see below for the best places to source OERs: