The document discusses a client + server hybrid architecture for applications using Vaadin. It involves layers of abstraction between the backend server and frontend web/JavaScript layers, with optional use of RPC, Java-to-JavaScript translation, and JavaScript. The architecture includes a widget on the client connecting via RPC to a component on the server, with state synchronization handled by the state object. Examples of implementations include specific widgets like HourList and views like BarView. Source code for a demo of the hybrid architecture is provided on GitHub.