While you can directly map the host filesystem to the container filesystem in the manner you describe, that's referred to as a bind mount, not a volume. Volumes

While you can directly map the host filesystem to the container filesystem in the manner you describe, that's referred to as a bind mount, not a volume. Volumes reside in the host filesystem as well but are solely managed by Docker. Outside of trickery requiring the use of bind mounts (I use one to share ~/.ssh between a host user and container user, for example), volumes are recommended.