Docker

What Is Docker?

Docker solves a fundamental problem: "It works on my machine." Developers build applications on their laptops, which behave differently in production due to dependency differences, configuration variations, or OS versions. Docker packages the entire application—code, dependencies, configurations—into containers that work identically everywhere.

Containers are lightweight virtual environments that share the host OS kernel (unlike virtual machines which emulate entire OSs). This makes containers efficient: minimal overhead, fast startup, low resource consumption. A single server can run thousands of containers. This efficiency enabled the microservices and cloud-native revolutions.

Docker provides a standard image format and registry system. Developers define applications in Dockerfiles (like code-as-infrastructure), build images, push to registries (like Docker Hub), and run in any environment supporting Docker. This standardization transformed how applications are deployed.