Suggest an editImprove this articleRefine the answer for “What is a Docker image?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)A **Docker image** is an immutable filesystem template from which Docker starts a container. **Key point:** a Docker image is a reusable, layered template that lets an application run reproducibly in a container.Shown above the full answer for quick recall.Answer (EN)ImageA Docker image is an immutable filesystem template from which Docker starts a container. The image contains everything the application needs to run: dependencies, system libraries, configuration, binaries, environment variables, and startup instructions. ### **Key properties of a Docker image** 1. **Immutable** - an image cannot be changed after it is built; any changes happen by creating a new layer. 2. **Layered structure** - an image consists of layers (each `Dockerfile` instruction creates a new layer). This saves space and speeds up builds. 3. **Reusable** - one image can be used to run many containers. 4. **Portable** - an image can be transferred and run on any machine that has Docker. ### **Relation to a container** - **Image = template** (like an ISO image or snapshot) - **Container = a running instance of an image** ### **Where images are stored** - locally on the machine; - in a registry (for example, Docker Hub, GitLab registry, ECR, etc.). **In one phrase:** a Docker image is a reusable, layered template that lets an application run reproducibly in a container.For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.