Alexa! Show me the money! I don't know what will happen if you give an Amazon Echo Show that command; she'll probably be like, Sorry, I don't understand, which is pretty much her Echo audio version self's response to everything I ask or tell her. But if you have more normal requests, like Show me my sleeping baby and Show me the lyrics to "The Humpty Dance", this video-added version of Amazon's smart speaker and voice-controlled virtual assistant is at your eyes' service.
Echo Show adds visuals, and a touchscreen, to some of Alexa's existing capabilities--scrolling song lyrics as music plays, pulling up weather forecasts on the Show screen--plus adds new features, such as playing YouTube videos and video flash briefings, and allowing owners of Echo Shows or the Alexa App to make hands-free video calls to one another.
The range of Echo-compatible smart home devices also grows with Show to include Ring front door / security cameras and Arlo baby monitors. Light and thermostat control via WeMo, Philips Hue, ecobee, etc. remain.
The Echo Show is a standalone device, with its own speakers and 8 at-your-service-sir microphones, so you don't need to own an Echo the First or Echo Dot already to use it. Of course, if you do have one of those, you'll end up with Alexa sisters, the younger prettier and more popular than the elder. You can keep them both and Echo out in different rooms (your existing settings, preferences, playlists automatically upload to a new Echo device linked to your Amazon account, but you can't sync them to, say, play music or set a timer together) or you can sell the old ugly Alex on Craig's List.