Open Educational Resources are 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. https://hewlett.org/strategy/open-educational-resources/
Open Educational Resources vs. Open Access.
Open Educational Resources (OER) are freely available online materials that anyone can use for learning and/or teaching. Examples are courses- including MOOCs (Massive Online Open Course), lectures, teaching materials, assignments and various other resources. OERs are available in many different formats compatible with online usage most obviously text, images, audio and video.
Anyone with internet access can access and use OERs; access is not dependent on location or membership of a particular institution. OERs are particularly useful for researchers, teachers and learners. Educational institutions and providers enhance their websites by creating and maintaining access to OERs and service providers such as iTunes U, SlideShare, YouTube and Jorum also have many OERs to offer.
Open Access (OA) refers to freely available content permanently online such as scholarly articles and journals. These resources can be reused and there is some scope for alteration. OER, on the other hand, encourages remixing and redistribution of the resource and covers a much wider range of materials. http://libguides.unisa.ac.za/c.php?g=355663&p=3473210