Video Ad Serving Template (VAST)
The Video Ad Serving Template (VAST) is a 3PAS standard for in-stream video established by IAB, allowing a publisher that supports VAST to play any VAST-compliant ad. In the past, each website had its own video player with its own look and functionality. The VAST standard specifies an XML file capable of holding a variety of resources, including links to video files, companion ads, non-linear banners, and tracking URLs.
For more information on VAST, visit IAB.