How would you provide an overview of the Vaadin architecture?

Vaadin consists of a server-side framework and a client-side engine. A developer creates the UI using the components, and Vaadin takes care of sending the UI state to the browser and rendering it there. The client-side engine captures user interaction and sends it to the server as needed. User interaction is can be reacted to by registering event listeners for the components. This makes it easy to separate the user interface from the business logic.