Open Educational Resources (OER) are educational materials like textbooks, videos, and tests that are in the public domain or licensed under Creative Commons, allowing free use, adaptation, and sharing. OER use Creative Commons licenses that allow creators to retain ownership while permitting their work to be used, adapted, reused, or remixed. Benefits of OER include being free, customizable, able to be shared, drawing from many sources, and promoting collaboration, while challenges include licensing variations, quality control, lack of consistent backing over time, and difficulty finding up-to-date resources.