juniorDocker
Explain the difference between a Docker Image and a Container.
Updated Apr 28, 2026
Short answer
An image is a static template (read-only); a container is a running instance of that image (read-write layer).
Deep explanation
Docker leverages Linux namespaces and cgroups to provide isolation. Unlike VMs, there is no hypervisor layer overhead, allowing for near-native performance and rapid startup times.
Real-world example
A developer wants to ensure their app runs exactly the same on their laptop as it does on a colleague's machine.
Common mistakes
- Confusing 'EXPOSE' with port publishing ('-p').
Follow-up questions
- What is a 'layer' in Docker?