# Docker Images

**Images** are blueprints for containers: layered filesystem snapshots plus metadata. Run `docker run` to start a container from an image; it starts instantly with everything pre-configured. Images are pulled from registries like Docker Hub and stored locally for reuse.

```bash
$ docker images              # list local images
$ docker pull <image>        # pull an image from a registry
$ docker rmi <image>         # delete an image
$ docker tag <image1> <image2> # retag an image
$ docker search <image>      # search Docker Hub
```

Each image has a name and tag (e.g., `ubuntu:latest`). The tag is usually a version or variant; `latest` is the default. Images are built in layers, where each layer adds or modifies files on top of the previous one. Layers are cached—rebuilding reuses unchanged layers, making builds fast.