UNESCO defines OERs as:
“Teaching, learning and research materials in any medium, digital or otherwise, that reside in the public domain or have been released under an open licence that permits no-cost access, use, adaptation and redistribution by others with no or limited restrictions”.
The focus of these resources is re-use. There are many repositories of OERs around the web that enable discovery, sharing and re-use.
Open Access refers to scholarly material that is freely available under an open licence and usually found in Open Access journals and institutional repositories.
Open Educational Resources are teaching resources that are freely available under an open licence and are typically reusable. The two are closely related and the key differences are the adaptation of resources allowed with OERs and the broader range of resources that are thought of as OERs.
For more information on Open Access see the Open Access Guide.