How do you use this app? – EARTH 3D | Ultra real planet Review

I was rather fascinated by the concepts and the high reviews gave me good feelings about this app. First I downloaded this app then I tapped on the get the weather which apparently was a whole other app then I put the weather on the widget which it is but this is listed under live wallpapers I'm not really sure what this does. Does this just run in the background of the weather app I just don't understand. . Why then do I need to apps for one widget. 
Review by woundrn1992 on EARTH 3D | Ultra real planet.