OER (Open Educational Resources) refer to textbooks, videos, curriculum, and images that are freely available online for students and teachers without cost. The document discusses the benefits of using OER, such as free access to quality materials, cost savings, and opportunities for interaction and sharing work globally. Some challenges of OER mentioned include information overload due to the large number of available resources, ensuring the quality and accuracy of online content, and selecting resources that truly enrich the curriculum rather than just expanding it. The document concludes that OER can be valuable tools for teaching and learning if used properly by competent educators.