The William and Flora Hewlett Foundation defines Open Educational Resources as "teaching, learning and research materials in any medium – digital or otherwise – that reside in the public domain or have been released under an open license that permits no-cost access, use, adaptation and redistribution by others with no or limited restrictions."
The 5 Rs of Open
The Open Education movement is built around the 5Rs of Open. These represent the gold standard in openness:
Retain – the right to make, own, and control copies of the content
Reuse – the right to use the content in a wide range of ways (e.g., in class, in study group, on a public website, in a video)
Revise – the right to adapt, modify, or alter the content itself (e.g., translate the content into another language)
Remix – the right to combine the original or revised content with other open content to create something new (e.g. mashup)
Redistribute – the right to share copies of the original content, your revisions, or your remixes with others (e.g., give a copy of the content to a friend)