What is OER?
The Hewlett Foundation and Creative Commons define Open Educational Resources, or OER, as "teaching, learning, and research materials that are either (a) in the public domain or (b) licensed in a manner that provides everyone with free and perpetual permission to engage in the 5R activities– retaining, remixing, revising, reusing and redistributing the resources." (https://hewlett.org/strategy/open-education/)