This document discusses Netzke, which allows building rich web applications by combining Rails and the Sencha JavaScript framework ExtJS. It notes that Sencha is a well-maintained cross-platform RIA framework, while Netzke provides a clean interface between Rails and Sencha and pre-fabricated UI components so developers don't have to write everything from scratch. Netzke is best suited for data-intensive applications like reporting, ERP, accounting, and admin backends that can replace desktop or Excel applications.