Docker is a platform for building, distributing, and running containers consistently across environments. It uses images—snapshots of a file system with an application and its dependencies—to create isolated runtime environments. Docker allows developers to replicate production setups on their local machines, reducing environment related bugs. Images are defined using Dockerfiles, which specify system packages, build steps, and startup commands. Docker made containerization accessible to mainstream development and became foundational to cloud native architectures. Many CI/CD workflows build and push Docker images to registries before deploying them.
how it works
Docker uses a daemon that manages images, containers, and networking. When you run a container, Docker creates isolated namespaces for processes, networking, and file systems. Containers can expose ports so they can communicate with each other or the outside world. Docker Compose lets teams run multi container setups with databases, caches, and application services in a single configuration. On servers or orchestration platforms, Docker images are pulled from registries and started identically across machines. Docker’s layering system allows images to reuse base layers efficiently, reducing storage and download size.