Video Multiple Ad Playlist (VMAP), which is an XML template, helps advertisers to have control over the ad inventory displayed in their content. VMAP allows them to define the total number of ad breaks in a video, which also include where they want to be played in a video, the duration of each ad, the number of ads in each break, what type of ads, and the order of the ads.
It is important to know that VMAP does not serve the ad since the ads are served via ad servers. VMAP works with VAST in a way that VMAP provides the playlist of ad breaks, and VAST fills the ads in these breaks.
In short, VMAP allows you, as an Ad Manager publisher, to control the inventory easily across many partner sites and communicate with other partners through ad break structures.
With VMAP, enjoy your many ad-ing-s in one video.