You may be wondering what defines an OER compared to other resources you might use for teaching and learning. Here I describe the differences among the most common resources used in the classroom, listed from most to least restrictive.
All creative output receives an all rights reserved copyright license by default unless explicitly stated otherwise. In this case, the author, authors, or publisher reserves the exclusive right to distribute, perform and create derivatives of the material they own. US copyright law grants some authorized uses of materials under copyright without receiving permission of the copyright owner originating from the fair use doctrine and the Technology, Education and Copyright Harmonization (TEACH) Act of 2002. Generally, published materials under traditional copyright can be purchased for individual use. Some materials (e.g., websites) are free to view but retain an all rights reserved copyright license.
Library licensed material, or LLMs, are published resources (books, articles, videos, data, etc.) assigned an All Rights Reserved copyright license. Access to these resources is sold to libraries who pay a one-time-fee or an annual subscription to make the material available to library-affiliated users. Access is limited and may disappear based on vendor, publisher, or library decisions. A LLM is no longer available to a user after their affiliation with the library ends (e.g., when a student graduates or an employee retires). LLMs are licensed to be used exclusively by the end user and can't be shared outside exceptions for the fair use doctrine. These materials appear free to affiliated users, but access is purchased by the university.
Open access materials, or OA, are free digital published resources (mainly scholarly books and articles) existing outside the confines of the traditional publishing structure, although still often published by traditional publishing companies. The purpose of OA is to disseminate research quickly, publicly, and freely. OA resources are almost always available online on the open web and are also often found within library databases (you might recognize the orange open lock logo symbolizing OA). These materials can be downloaded, printed, and shared freely. There are no restrictions on who can access OA materials.
Open Educational Resources, or OER, are digital resources used during the teaching and learning process, most often authored and designed by faculty teaching the course for which the resource is used. OER are published by an individual, a library, an institution, or, less frequently, a company. OER must have an open license that allows end users to create and share derivates of the original work. Often OER remain under copyright protection with extra use allowances provided by the author.
Resources in the public domain are not protected by copyright law and are owned by the public rather than by a person or publisher. In the United States, these resources most frequently have either an expired copyright license or the original author intentionally released their work to the public domain (often seen with a CC-0 mark).