MRAID full form is “Mobile Rich Media Ad Interface Definitions”
VAST is used as a standard for video player
MRAID is used as a standard for mobile rich media (video) advertising
This standard defines the communication between the video player and the ad server which basically controls the placement of video advertising
The IAB MRAID standard allows rich media advertising materials together using standard technology to deliver the apps without having to integrate advertising in the platform-specific programming of the app.
VAST also ensures that video advertising can also be linked via a redirect
MRAID ensures to run almost all kind of rich media ads on mobile apps
VAST is a script for the video ad which gives consistent instructions to the video player on how to handle an ad