More than a device
Alexa is the voice-interface for some of Amazon's new devices. You can talk to her and she understands. Ask her questions about movies, capitals, or famous people, and she knows. Ask her what 142 divided by 6.7 is, and she will tell you 21.19. Ask her how to spell charisma, and then ask her what it means. Ask her to play songs on countless music channels, and she will offer them to you (if you are a Prime member). Upload your entire music collection to her, and she will stream it to you anywhere. She can read countless audible books, turn on the lights in your house with a simple command, identify the best pizza place in your neighborhood, and can read you the headlines from the news services you trust the most.
She is more than a device, though the way you access her is through one of several powered speakers that Amazon offers for your desktop.