Open educational resources (OERs) are materials that are free of charge, and free of most copyright and licensing restrictions.
“Many researchers release their previously unpublished work under a Creative Commons (CC) license, that allows you to authorize some uses of your work, while preventing others... For more information, please visit the websites for Creative Commons.” (Open Access, Montclair State University, http://montclair.libguides.com/openaccess)
OERs can be used to customize course materials and are often used to save students the cost of buying an expensive textbook.
Open Educational Resources can take the form of any materials associated with teaching and learning, including:
The following "Quick Guide to Open Educational Resources" is from Georgia State University Library at http://research.library.gsu.edu/openeducation