This guide demonstrates how to build a sample backend app in Node.js that uses 100ms REST APIs for creating rooms, generating Auth Tokens, and getting usage analytics for the latest session in the room. The application consists of two components: client (frontend) and server (backend). The server communicates with 100ms REST APIs to perform various operations. Key terminologies like Room, Auth Token, and Session are explained. The guide provides step-by-step instructions for setting up the environment, creating services for token management and API calls, and implementing request handlers for different endpoints. Finally, it suggests deploying the app on Render for free.