Imagine you want to send a project to a friend, and it works perfectly on your computer. You send the files, but when your friend tries to run it — nothing works. Their system is different, some required programs aren't installed, or the setup isn't the same. That's where Docker comes in.

Think of a container like a box with a toy inside that already has batteries and instructions. Wherever you open it, the toy works just like it should.

Key Docker Concepts

All these concepts are essential for successfully deploying your application. They work together in the following order, as shown in the diagram below:

Docker simplifies software deployment by using images, containers, and registries. A Docker image packages an application with all its dependencies to ensure consistency across environments. When run, the image becomes a container, an isolated, lightweight runtime environment. Docker registries like Docker Hub allow developers to store, share, and access these images, enabling fast, scalable, and portable application delivery.

Why Use Docker in DevOps?

Docker is an important tool in CI/CD pipelines because it helps make software builds and deployments more reliable. It allows developers to create the same development environment on different computers, which reduces problems caused by differences in systems.

By packaging the app together with everything it needs, Docker makes it easier to move the software smoothly from development to testing and then to production. Docker works well with CI/CD pipelines, enabling automated testing and deployment.

In short, Docker helps ensure that applications run the same way in development, testing, and production environments.