“Open access” refers to resources online—usually academic resources—that are freely available. When trying to find scholarly articles online, you will want to find open access journals or open access articles within more-traditional scholarly journals. Google Scholar and Microsoft Academic Search don’t do a great job of helping you limit your search results to those resources that you have access to, so it can be frustrating at times when using them to conduct research. On the other hand, PubMed and ERIC do provide ways for you to limit your search results to those resources that are freely available. Another resource to check out is The Digital Commons Network, which is a directory of open access articles and resources from universities and publications that you can access freely.
Remember, for any resource that you find online that you cannot access or that has a paywall, consult with a librarian to see if there’s another way for you to access the resource freely. It might be possible for the library to get you access through interlibrary loan, which is when libraries cooperate with each other to provide access to resources that one library may not have, but another library does.
OER stands for Open Educational Resources. OER are materials that can be used and adopted in place of traditional course materials in order to promote equitable access to education as there is no cost for the student or faculty to use OER. That means if your professor uses an OER textbook, you can access that textbook for free online. This is an OER textbook, as an example.
OERs are not limited to textbooks. They could be articles, documents, movies, images, and more. What defines them are the permissions or license that comes with them. Though we won’t dive into all the aspects of licensing and copyright permissions, basically, if the material is licensed so that you can share, revise, and keep a copy of the resource freely, then you have an OER. OER is different than open access in this regard, because open access only allows you to access the resource.