Open Educational Resources (OER) are openly-licensed, freely available educational materials that can be modified and redistributed by users. They can include any type of educational resource, from syllabi to full courses.
The definition above was adapted from The OER Starter Kit by Abbey K. Elder and is licensed under a Creative Commons Attribution 4.0 International License.
The terms "open content" and "open educational resources" describe any copyrightable work (traditionally excluding software, which is described by other terms like "open source") that is either (1) in the public domain or (2) licensed in a manner that provides users with free and perpetual permission to engage in the 5R activities:
These guides include information for entry level users, including explanations of key concepts, introductions to open licenses, and tips for differentiating OER from other kinds of free content.