OER refers to teaching, learning, and research resources that are freely available or have an open license allowing reuse. OERs include full courses, materials, modules, textbooks, videos, and other tools. They provide benefits like lower costs for students, less prep time for teachers, and access to teaching ideas. However, not all subjects or courses have quality OER content available, some resources rely on temporary grant funding, and users need to understand licensing. Overall, OERs are a valuable tool for educators by potentially saving time and allowing focus on other areas.