"Echo" seems to be a voice-controlled interface (is that an oxymoron?!) to stuff that is on the web, especially from Amazon. At least that's the 'message' I get from their ads, when I accidentally hear/see one.
How accurate is my opinion? Is it limited to things you store/have at Amazon, including their servers? Or can you connect to other things on the WWW?
Sorry, I forgot to answer you.
Voice-controlled to stuff on the web: same as Siri is. Alexa will look up info, find recipes, shop at Amazon and other places (I know you can order flowers) -- but I'm guessing that the vendors have a deal of some kind with Amazon. She'll make lists, play radio stations, play music (and I can upload non-Amazon purchased music to my account). I get a daily flash news briefing and I can pick the sources. She reads books from my Kindle, but I don't know if she'll read books purchased from other sources. I've had her look up and read Bible verses/passages to me, but she only reads KJV as it's public domain; so she might read other public domain books. She plays word games, tells corny jokes, and there are skills I've never explored: movies, tv, learn languages, smart home stuff, etc, etc. Pretty much if Siri does it, so does Alexa—so she'll connect to non-Amazon stuff on the web.
My one gripe was the day I asked her who was officiating at an NFL game. Now I was watching delayed via a recording, so it was only the 1st quarter to me. Well, Alexa misunderstood and told me the final score of the game. I wasn't a happy football fan at that point—but I've had Siri do the same thing; so I now always look stuff up by typing a specific question into the browser on my iPad, and I've avoided any more spoiled games. Other than when my team fails to show up and play.