What is a Commons? 
What is Wikimedia Commons? 
The Wikimedia Commons (also called "Wikicommons", or just "commons") is a repository of free content images, sound and other multimedia files. Like Wikiversity, it is a project of the Wikimedia Foundation. It provides a common resource repository to all the various Wikimedia sister projects in any language.
The files uploaded to the Commons repository can be used like locally uploaded files on all other projects on the Wikimedia servers in all languages, including Wikipedia, Wikibooks, Wikisource and Wikinews, or downloaded for offsite use, as all of the content is either in the public domain or released under free licenses such as the GNU Free Documentation License.
Projects for collaboration between Wikiversity and Wikimedia Commons 
Almost all Images and other media that appear on Wikiversity are embedded here from the Wikimedia Commons.