This document discusses the relationship between mobile app development and backend services. It explains that mobile apps need scalable backend services to handle data storage, user management, notifications, and other tasks that mobile devices cannot handle alone. It then introduces the concept of backend as a service (BaaS), where developers can use third-party services to access common backend functions without having to build their own backend infrastructure. The document provides examples of startups that are using BaaS to develop their mobile apps.