The video below provides an useful introduction to what Open Educational Resources (OERs) are:

OECD and UNESCO provide useful definitions for OERs:

“Teaching, learning and research materials in any medium, digital or otherwise, that reside in the public domain or have been released under an open license that permits no-cost access, use, adaptation and redistribution by others with no or limited restrictions.” (UNESCO, 2012).

“Digitised materials offered freely and openly for educators, students and self-learners to use and reuse for teaching, learning and research.” (OECD, 2007).