Open Educational Resources (OER) are teaching and learning materials that are made freely available under public licenses. Like Open Content, they generally fall under copyright, but are made available by the holders of copyrights for more or less free use. Their use must comply with the obligations of the applicable open content licence. The basic idea is that "open" does not mean "free of charge", but "intended for free use".

An open educational resource may be copied, posted and distributed without the need to notify the copyright holder. Furthermore, open licences allow use without licence fees. Nevertheless, OER may well cost money, e.g. if the content is sold as books.

The possibility of free dissemination allows the teaching and learning content to be adapted, optimised, further developed and freely shared by everyone. The example of Wikipedia shows how great the potential of this decentralised generation of knowledge and knowledge products is. In the ideal case, the result is that knowledge is increased in cooperation, from which the entire society benefits.

As OER, different forms like courses, course applications, course modules, but also text files, pictures, audio, video, simulations etc. can be understood. Also included are tools such as learning management systems or training materials for the use or quality assurance of OER. In general, OER can be differentiated by material type (software, publications, courses, etc.) and by media format. In context of learning materials, software applications and standards are needed to support the development, use and re-use of learning content (see www.e-teaching.org/didaktik/recherche/oer).