This document discusses building real-time web applications and introduces SignalR as a library that simplifies creating persistent HTTP connections for real-time functionality. It describes how older techniques like polling and long polling have disadvantages, while newer techniques like web sockets have limited browser support. SignalR abstracts these complexities by automatically negotiating the best transport and allowing real-time functionality to be easily added to applications. It also enables scaling out applications across servers and backing services. Demos and components of SignalR are presented, along with how it provides a fallback mechanism to support older servers and clients.