How does a dynamo work?

Hey:)

I have a physics test tomorrow and I don't know the topic because I was sick last week…

Here's my question: A dynamo is an alternating current generator… Does the rotor in the coil rotate in complete circles or does it only move from left to right? 🙃

PS: If my assumption is completely wrong, could someone please explain to me exactly how this works? I'm completely lost right now.

Thank you very much,

Sophia