In this Day 08 session, I start from a super beginner-friendly place and then move step-by-step into deploying containers on AWS. First, I explain why Docker became such a big deal—because of that classic “it works on my machine” problem. Apps depend on OS settings, libraries, and software versions (like Java 24 vs Java 21), and Docker solves it by packaging your app plus everything it needs into a portable container. I also break down the core Docker concepts: image (blueprint/recipe) vs container (the running instance), and why registries exist to store and share images (public or private), like Docker Hub. Then I map those Docker concepts directly to AWS: ECR is your Docker registry on AWS (Elastic Container Registry), ECS is the service that runs your containers (Elastic Container Service), and Fargate is the ECS launch type that lets you run containers “serverlessly” (meaning you don’t manage servers). After that, I do a hands-on demo: I create an ECR repository, pull the official NGINX image locally, authenticate Docker to ECR, tag the image with the ECR repo URI, and push it into ECR. Finally, I move into ECS, explain clusters as the environment where containers run, choose the Fargate option, and also show a real-world troubleshooting moment around the ECS service-linked role/permissions so you know what to check when AWS throws errors.