First Off The Tube (Lite) helps you board the Tube in order to be closest to your exits and interchanges at the chosen station. It incorporates a detailed database of each and every exit and interchange found on the Tube system and works perfectly well while you're underground as it needs no internet connection or GPS information. You can search by line, or just by the station name to find the station you're looking for.
The app also provides information on the closest stations to a number of London's tourist attractions.
The LITE version covers the ten busiest stations only, and a limited number of tourist attractions.
*** People, for those of you that mark the app down because 'there is no functionality in it': The app is supposed to show you that the full version can do certain things, and this is what it would look like, etc, so you'd not be buying a 'pig in a poke'. It helps you to judge if you like the design, looks, font size, etc. Also to actually help you on the most frequented stations! Thanks.