Open Access means unrestricted access and unrestricted reuse.
Open Educational Resources (OER) are teaching, learning, and research materials in any medium that reside in the public domain or have been released under an open license that permits their free use and re-purposing by others.
Open Access is part of a continuum ranging from completely closed, subscription/purchase only access to completely open, no barrier publishing. Open Access is not related to the quality of materials or the peer-review/non-peer-review status of the publications.
Most publishers own the rights to the articles in their journals. Anyone who wants to read the articles must pay to access them. Anyone who wants to use the articles in any way must obtain permission from the publisher and is often required to pay an additional fee.
Although many researchers can access the journals they need via their institution and think that their access is free, in reality it is not. The institution has often been involved negotiations around the price of their site license and re-use of this content is limited.
Paying for access to content makes sense in the world of print publishing, where providing content to each new reader requires the production of an additional copy, but online it makes much less sense to charge for content when it is possible to provide access to all readers anywhere in the world.
Advantages of using OERs include:
Disadvantages of OERs include: