Open Educational Resources (OER) are educational materials that are published under an open (usually Creative Commons) licence. An open licence allows free use, editing and redistribution, with no or only minor restrictions for others. Open Educational Resources are characterised by the fact that all users are permanently granted the following rights, which are referred to as the 5 Rs:

1. Retain 2. Revise 3. Remix 4. Reuse 5. Redistribute

Open Educational Resources have gained in importance in recent years, partly due to the high cost of textbooks, especially in the USA. In many subject areas, there are now a large number of freely available teaching and learning materials on the internet. Open Educational Resources are independent of type and medium and can include individual materials, but also complete courses or books. Other examples are curricula, course materials and exercises, textbooks, wikis, videos, multimedia applications or podcasts. MOOCs (Massive Open Online Courses) from universities and other educational institutions fall under this category, provided they are offered under an open licence. OERs are a building block for achieving Open Education.