What is Docker?
Docker is an open-source platform for building, shipping, and running applications inside lightweight, portable containers that package code and all its dependencies so the application runs reliably regardless of the host environment.
How Does Docker Work?
Docker simplifies the packaging and deployment of applications by using container images — read-only templates that define everything an application needs to run, including the code, runtime, system tools, libraries, and settings. A Dockerfile provides a script of instructions to build an image layer by layer. Once built, the image can be shared via registries like Docker Hub and instantiated as running containers on any machine with Docker installed.
Docker has become essential in modern development and hosting workflows. Developers use it to create consistent development environments that match production, eliminating "works on my machine" problems. In production, Docker containers are often managed by orchestration tools like Kubernetes or Docker Swarm that handle scaling, load balancing, and self-healing across clusters of servers. Docker Compose allows developers to define multi-container applications (such as a web server, database, and cache) in a single YAML file.