🐳 Free Docker course: understand containers in 40 minutes
Welcome to the most pedagogical Docker discovery course. In 7 short lessons, you will understand exactly what a container is, why Docker disrupted software development in 2013, and how it is actually used in companies in 2026.
What this course aims for: answering once and for all the questions "what is Docker?", "what is the difference between an image and a container?", "Docker vs virtual machine?" — without unnecessary jargon, with concrete analogies.
What this course does not do: teach you to type the docker run, docker build, etc. commands. That practical mastery is the subject of the Premium Docker Course.
What you will discover
Course content
| # | Lesson | Main objective | Duration |
|---|---|---|---|
| 1 | The problem Docker solves | Understand why the software world had a real problem before 2013 | 5 min |
| 2 | What is Docker? | Rigorous definition, shipping container analogy, brief history | 6 min |
| 3 | Image, container, Dockerfile: the trinity | Clearly distinguish the 3 fundamental concepts | 7 min |
| 4 | Docker vs virtual machine | The comparison that makes everything crystal clear | 6 min |
| 5 | The Docker ecosystem | Docker Hub, Compose, Swarm, Kubernetes, Podman, alternatives | 6 min |
| 6 | Real use cases | Where Docker is really used in 2026: dev, CI/CD, microservices, ML | 6 min |
| 7 | Recap and FAQ | Synthesis, answers to the 14 most frequent questions | 5 min |
| 8 | Quiz and attestation | Validate what you learned with 5 corrected questions | 3 min |
Is this course for you?
- You are a student, a junior developer, or in a tech career change, and you hear "Docker" everywhere without ever having understood what it is.
- You are a project manager, product owner or technical manager, and you want to understand your DevOps team's vocabulary.
- You have already run a copy-pasted
docker runfrom a tutorial, but you do not know what is really happening. - You are preparing a technical interview and want to be able to answer "explain Docker to me in one minute".
No technical prerequisites. Basic knowledge of Linux helps to grasp the magic, but is not mandatory.
The course plan at a glance
What you will know at the end
No commands to memorize. At the end of the course, you will know how to:
- Explain in one clear sentence what Docker is (and impress in an interview).
- Distinguish image, container and Dockerfile without hesitation.
- Answer "Docker or virtual machine?" with the real arguments.
- Understand Docker Hub, Docker Compose, and why Kubernetes exists.
- Recognize the cases where Docker is the right choice and the cases where it is not.
- Approach the Premium Docker Course confidently to move on to practice.
⏱️ Estimated duration
About 35 to 45 minutes of reading in total. Each lesson is self-contained — you can read one per day for a week, or go through everything in one sitting.
Prerequisites and recommended companions
Prerequisites: none formally, but two discovery courses prepare the ground perfectly:
- Linux Discovery — to understand why Docker is intimately tied to the Linux kernel (namespaces, cgroups).
- Discovering version control (Git) — to understand analogies like "Docker Hub is to Docker what GitHub is to Git".
Natural follow-up — to go further after this course:
- Kubernetes Discovery — orchestrating thousands of containers
- CI/CD Discovery — automating Docker deployments
- Premium Docker Course — practical mastery with exercises
Frequent questions in one answer
What is Docker in one sentence?
Docker is a tool that packages an application and all its dependencies into a standardized box called a container, which runs identically on any machine (developer workstation, server, cloud). No more "it works on my machine but not on the server".
Are Docker and a virtual machine the same thing?
No, they are two very different technologies. A VM simulates a complete computer with its own operating system — it is heavy (several GB) and slow to boot (several minutes). A container shares the host machine's kernel — it is light (a few MB) and starts in under a second. Lesson 4 compares everything in detail.
Image, container, Dockerfile: what is the difference?
- The Dockerfile is a recipe: a text file describing how to build an image.
- The image is the cooked dish: the result of the recipe, ready to serve. It is read-only.
- The container is the plate served on the table: a running instance of the image.
Lesson 3 develops this analogy in detail.
Is Docker free?
Docker Engine (the engine that runs containers on Linux) is open source and free. Docker Desktop (the graphical interface for Windows and macOS) is free for personal use and for small businesses, and paid beyond 250 employees or 10 million dollars in revenue since 2022.
Why Docker rather than installing the application directly?
Three reasons: reproducibility (the container runs identically everywhere), isolation (the application does not pollute your system), speed (you start a database, a web application, a full test environment in seconds). Real use case #1 shows it.
Is this course enough to be operational in a company?
This course gives you the complete conceptual understanding. To be operational (writing a Dockerfile, managing volumes, orchestrating with Docker Compose, securing, optimizing image sizes), you need the Premium Docker Course with its 30+ hours of practical content.
This discovery course explains how it works, without commands.
To type the real commands (docker build, docker compose up, volume management, networks, image optimization, security), move on to the Premium Docker Course — included in all our paid plans.
Other discovery courses not to miss
- Introduction to version control — the basics of Git
- Git in practice — team workflow, PRs, conflicts
- Linux Discovery — the OS of servers
- Kubernetes Discovery — orchestrating thousands of containers
- CI/CD Discovery — automating deployments
Ready? Start with lesson 1 →