The new service from Google will integrate a quick buying system called "Click-To-Buy" into youtube videos. The links once clicked bring you to Amazon’s MP3 store and iTunes where you can then buy the related song or media.
The new feature (ads) have gone live already in the U.S. and will expand beyond our borders once the service gets going. The service will include links to television, film, and publishing and will be on videos supplied via the owners of the content the service links to.
"Our vision is to help partners across all industries–from music, to film, to print, to TV–offer useful and relevant products to a large, yet targeted audience, and generate additional revenue from their content on YouTube beyond the advertising we serve against their videos" according to Google’s Blog.