The document discusses using Amazon EC2 for hosting applications. It covers key EC2 concepts like regions, availability zones, instance types, Elastic IP addresses, Elastic Block Storage, Elastic Load Balancing, and Relational Database Service. It provides guidance on choosing instance types, reserving instances, bootstrapping instances using images or scripts, and deploying applications with tools like Chef. The goal is to illustrate how to set up and flexibly scale an application on EC2 to support millions of daily users.