is a free knowledge base
that can be read and edited by humans
and machines alike. It is for data what Wikimedia Commons
is for media files: it centralizes access to and management of structured data, such as interwiki references and statistical information. Wikidata contains data in all languages
for which there are Wikimedia projects.
You can read the introduction to learn more about Wikidata.
See Wikidata in action: View the item listing all 286 editions of Wikipedia's Main Page.
If you'd like to test out the Wikidata software, please use the sandbox