A Video Viewer atom is simply a way to display either the media from a video object or from a video URL within a webpage.
How do I use it?
One of two ways:
As a standard atom on a page: When editing the user will be asked to browse for and select a video object. This will then render a standard video player from the video object's video source (i.e.: YouTube, Vimeo)
As a widget within a html field: This behaves in exactly the same way as the standard atom, however it allows the user to wrap text around it
It is also possible to render a video within a News Atom if a news article has an associated video.