What Is OER?
Open educational resources (OER) are free and openly licensed educational materials that can be used for teaching, learning, research, and other purposes.
There are different types of OER. OER generally includes any educational content that is shared under an open license.
OA stands for Open Access. Open Access means that the materials focus on sharing content but there are no underlying licensing requirements.
OCW stands for Open CourseWare. Open CourseWare's focus is sharing open content that is developed to teach a specific course.
I tend to use a general description of OER that includes any educational material that is free to use and can be incorporated into your lessons, units, or courses.