This document discusses single page applications (SPAs) and their architecture. It begins by explaining what SPAs are, noting that they are web applications that don't require full page refreshes and use client-side routing. The key building blocks of SPAs are then outlined as HTML5, JavaScript libraries, AJAX, REST APIs, and client-side routing. It also discusses specific technologies like AMD/RequireJS for module loading and the Model-View-Controller pattern using Backbone.js. The document concludes by advertising a demo of building a simple SPA.