This document discusses the evolution of web application development from monolithic applications to microservices architectures. It provides examples of how adding a new "follow" button functionality would differ between a monolithic app versus separate services. It then demonstrates a simple counter app implemented with Docker, Node.js, and Redis to illustrate the benefits of microservices like fault isolation, scalability, and easier debugging. The key advantages of microservices are discussed as isolation, immutability, and having each service focus on a specific problem.