What is cross-origin resource sharing?

An HTML5 cross-origin resource sharing (CORS) policy controls whether and how content running on other domains can perform two-way interaction with the domain that publishes the policy. The policy is fine-grained and can apply access controls per-request based on the URL and other features of the request.

For more information about CORS and how it works, refer to http://www.html5rocks.com/en/tutorials/cors/.