Cross-Origin Resource Sharing

Cross-Origin Resource Sharing, or CORS, is a set of security checks done by a web browser to confirm that the web page displayed is allowed to retrieve data from a different server. CORS issues often come up when dealing with APIs, particularly when data is being shared from several different sources. It is important to configure CORS settings correctly, open enough for a good user experience, but restricted enough to prevent requests for data from undesirable sources. CORS helps to prevent Cross Site Scripting and other similar attacks.

CORS Wikipedia