Mount a directory from the host to a container in Docker

Question

In a `docker-compose.yml`, what does the following `volumes` field do?
```yaml
volumes:
  - ./data:/var/data
```

Accepted Answer

It mounts the `./data` directory on the host to `/var/data` in the container.

Answer

It copies the contents of the `/var/data` directory on the container to `./data` on the host.

Answer

It mounts an external volume named `./data` in the container at `/var/data`.

Answer

It creates a volume named `./data` and mounts it on `/var/data` in the container.

Question from the Docker compose test