Open Educational Resources (OER) are course materials that are free for teachers and students to access and use. These include textbooks, lesson plans, activities, worksheets, and more.
Many OER also come with creative commons licenses, which are copyright permissions that allow instructors to modify, adapt, and edit the text, which gives you greater flexibility and control over the content.
Materials may either be created as OER or they may be licensed by the school, with one purchase providing access to all students.