Docker

What is Docker

Docker is a platform for building, shipping, and running applications inside isolated containers. A container packages the application code together with all its dependencies (libraries, runtime, system configuration), ensuring it runs identically across any environment: development, staging, or production.

How it works

Docker uses a Dockerfile to define the build steps for an image. That image is an immutable package containing everything needed to run the application. Running an image creates a container, which is an isolated process with its own filesystem, network, and process space. Docker Hub and private registries allow teams to distribute images across environments. Docker Compose simplifies defining multi-container applications (for example, app + database + cache) in a single YAML file.

Why it matters

Docker eliminated the classic “it works on my machine” problem. By standardizing how applications are packaged, development teams can deliver predictable, reproducible software. It also drastically reduced deployment times and the complexity of configuring environments. Docker is the foundation on which orchestration platforms like Kubernetes are built.

Practical example

A development team works on a Node.js application with PostgreSQL and Redis. With Docker Compose, every developer spins up the full environment with a single command: docker compose up. The same set of images deploys to staging and production without modifications. When a new team member joins, their development environment is ready in under five minutes instead of the hours manual setup used to require.

Related terms

• Kubernetes - Platform that orchestrates Docker containers at scale
• ECS (AWS) - Amazon’s managed service for running Docker containers
• DevOps - Development and operations practices that Docker enables

Last updated: February 2026