Intro & Concepts — Module Overview

Why Docker?

Every developer has heard it: “It works on my machine.” The application runs perfectly in development, then breaks in staging or production because of a different OS, a mismatched library version, or a missing environment variable. Docker eliminates that gap by packaging your application together with everything it needs — the runtime, dependencies, and configuration — into a single, portable unit called a container.

With Docker you get:

Consistent environments — the container runs identically on a laptop, a CI server, and a cloud VM.
Isolation — each container has its own filesystem and process space, so applications do not interfere with each other.
Speed — containers start in milliseconds, not minutes.
Reproducibility — a Dockerfile is a precise recipe; anyone who builds it gets the same image.

What this module covers

Lesson	What you will learn
This page	Problems Docker solves, first container
What is Docker?	Architecture: client, daemon, images, registries
Containers vs VMs	Kernel sharing, lightweight isolation, when to use which
Install & Verify	Installing Docker, verifying installation
Your First Container	Interactive + detached containers, docker ps, docker stop

Your first container

The fastest way to confirm Docker is working — and to see what happens when you run a container — is the official hello-world image. Docker will pull the image from Docker Hub if it is not already cached locally, start a container, print a confirmation message, and exit.

docker run hello-world

Try it now using the interactive playground below:

docker run hello-world