Open educational resources, known as OER, are free, accessible and open license documents and media used for teaching, learning, assessing and researching. OER may include full courses, course materials, modules, textbooks, streaming videos, tests, software, and other tools, materials and procedures.
The term was first used at a UNESCO 2002 Forum on Open Courseware. So, it's hardly surprising that OER is part of a global open content movement that allows instructors to reuse, review, remix and redistribute those materials.
Why OER is important
Edutopia's Open Educational Resources Guide
notes quality OER saves individual instructors from re-inventing the wheel. You reduce time and effort to resource development, plus might improve available material and best practices through collaboration.