Alexa / echo dot novice. Help please!

[CoddledAsAMommet]

We don't have any Alexa type gadgets but I've been thinking of getting one (a dot?) For my nearly 12 year old DD.
Can I have a dot as a stand-alone gadget or do I need an Alexa?
If your children have one, what do they use it for? I see there are games available (with buttons?) But not sure what these would be.
Would she need an App on her phone to use it? Is it a flash in the pan?
Thanks!!

I have an Echo, and my son has an Echo Dot. He uses it mostly for books, and music. She doesn’t need to have the app, you can have it on your phone, it also lets you know everything that has been asked of Alexa so quite handy.