OER are provided free of charge and are openly licensed. In contrast, resources that are free of charge but are not openly licensed are not OER. Such resources may have restrictions that prohibit remixing or revising content, may be free only temporarily, and may have restrictions on sharing.
There are two conceptions of "free"—free in terms of price and free in terms of the freedoms allotted to the user. OER is free in both senses of "free," while resources that are free of charge do not necessarily allow the user freedom in engaging with the material.
While many OER
are available online, OER is any resource, regardless of format, that is free of charge and openly licensed. Thus OER can refer to hardcopy texts, video, audio, and handouts, as well as online resources.