Open Access (OA) refers to removing barriers such as "paywalls". Open Access initiatives seek to make research articles and other works easy to find and read, for free. It does not address copyright, but rather the methods of funding and accessing the research or other works.
Example: An open-access journal article published in an open-access or hybrid academic journal.
Open Educational Resources (OER) are works that creators have "opened" by adding a Creative Commons or other License that removes some copyright restrictions. These resources allow others to "retain, reuse, revise, remix, and redistribute" without needing to ask for permission, as long as the work is attributed to the copyright owner, giving credit where it is due.
Examples include: Open textbooks, lesson plans, simulations, chapters, presentation slides, notes, etc.
For more information on publishing open access or incorporating OER into your classroom, contact Jenny Roberts-Reilley, Open Resources & Scholarly Communications Librarian, robertsreilley@susqu.edu.