The Videowall is meant to provide a massive preview of your entire catalog at once. It loops through all your video scenes in all your videos from start to end, all in the same window if it fits.
The Videowall is a great tool for quick overviews and can be used to get a first grasp of the content of the catalog holds for content or if you are looking for something special among lots of videos. For example if you have over hundred of long surveillance videos you might want to look at them all at once just to figure which ones to really look into.
Once you find something interesting simply double click to get all the video scenes(Video scenes or thumbnails are shortcuts to a time in a video) for that video. From the Video Scenes window you can start playing directly from each scene that you find interesting, just by clicking them.