It's basically a box that plugs into a television and provides internet/website access plus other so-called 'smart' features that are often only available with modern televisions. This means that you can watch YouTube videos and other online content such as the BBC's iPlayer (perhaps) on your television as well as browse websites and access Facebook, Twitter, etc., using your television as a display. You can play games like Angry Birds and possibly also install other applications as well.
From what I can tell, the Evolve uses some form of Android operating system (basically the same as many 'smartphones'), but there may be limitations as to what the Evolve is capable of running compared to a decent modern smartphone . I may be wrong but I think that the Evolve is capable of running Adobe Flash for video playback, so make sure that Flash is enabled first if anyone's having trouble with video streaming. You might even have to download update(s) to make this feature work properly (if required).
My relatively new television can supposedly do many of these things as standard but I haven't yet bothered to set it up yet because I have a perfectly decent computer in the same room as the television :smile:
If you're thinking of buying an Evolve or something similar, please don't pay too much money for one because the price of such a box has fallen dramatically in recent months - I think you can now get something similar for less than £50 - and the technology is improving all the time as well.