What does the `docker pull` command do?

The docker pull command is used to download a Docker image from a Docker Registry, which is a repository that stores Docker images. When you run this command, Docker retrieves the specified image (and any layers it depends on) from the Registry to your local machine, allowing you to use it to create containers.

This command is fundamental for obtaining images that have been published and are available on public or private registries, such as Docker Hub. Once the image is downloaded, you can run it to create and operate a container based on that image.

The other options do not accurately describe the function of the docker pull command. Starting a new container, updating an existing image, or removing an image involves different Docker commands that serve distinct purposes within the Docker ecosystem. Such commands include docker run for starting containers, docker pull can indirectly update an image if a newer version is pulled, and docker rmi for removing images from local storage.