A simple answer will suffice. I'm looking to build a new website and I like the expandability and code sharing happening in the Dart frameworks, but I don't really understand how the two frameworks differ on a fundamental level. The answer can be as in-depth as you like, but I'm really just looking for the layman answer.
AngularDart is, well, Angular in Dart.
Flutter, on the other hand, is a lot closer to React.
Flutter uses the Component pattern from React but is manipulated without HTML/CSS, and instead uses canvas/custom elements.