Affordable Course Materials are educational materials that have been made freely available, or at a low cost. The definition is intentionally vague because what may be freely available to one group (e.g. college students) may not be free to another group (e.g. corporate employees). The intent of OER is to make resources available to the broadest possible constituency for the lowest cost possible.
OER fall into many categories including the following (select a tab above for resources):