# Docker
Confidence: high
Last verified: 2026-05-22
Generation: human_only


## TL;DR

Docker is an open-source platform for developing, shipping, and running applications in lightweight, isolated containers. First released in 2013 by Solomon Hykes at dotCloud, Docker revolutionized software deployment by packaging applications with all their dependencies into portable images that run consistently across any environment. As of 2026, Docker is used by over 15 million developers and is the foundation of modern cloud-native infrastructure.

## Core Explanation

Docker containers are lightweight virtualization units that share the host OS kernel but run in isolated user spaces with their own filesystem, networking, and process tree. Unlike virtual machines, containers don't need a full guest OS — they start in milliseconds and consume minimal overhead.

Key components:
- **Dockerfile**: Declarative script defining how to build an image
- **Image**: Read-only template with application code, runtime, libraries
- **Container**: Runnable instance of an image
- **Registry**: Repository for storing and distributing images (Docker Hub, ECR, GCR)
- **Docker Compose**: Multi-container application orchestration

## Further Reading

- [Docker Docs](https://docs.docker.com/): Official documentation
- [Docker Hub](https://hub.docker.com/): Container image registry