An Open Education Resource (OER) is a teaching resource that can be used and reused freely for educational purposes because the author(s) have freely released the work to the public for that purpose - usually using one of the six types of a Creative Commons License.
"The 5 Rs":
In order for a resource to qualify as Open Access, users should be able to 1)Reuse – use the content in a wide range of ways (e.g., in a class, in a study group, on a website, in a video). 2) Revise – adapt, adjust, modify, or alter the content itself (e.g., translate the content into another language) 3) Remix – combine the original or revised content with other open content to create something new (e.g., incorporate the content into a mashup) 4) Redistribute – share copies of the original content, your revisions, or your remixes with others (e.g., give a copy of the content to a friend) and 5)Retain – make, own, and control copies of the content.
(This material is based on original writing by David Wiley, which was published freely under a Creative Commons Attribution 4.0 license