Open Educational Resources (OER) are teaching and learning materials that are freely available for anyone to use, adapt, and share. These resources can include textbooks, videos, lesson plans, and even entire courses. The goal of OER is to make education more accessible and affordable for students and educators around the world. By using OER, teachers can customize their lessons to better fit their students' needs, while students can access high-quality materials without the burden of high costs. This movement is supported by organizations like Creative Commons, which provides licenses that allow creators to share their work openly and legally.