docker will allow you to view the various commands and management commands supported by docker. The docker client talks to the docker daemon via it's REST API over a UNIX socket or HTTP. Each of the management commands represents a resource on the docker daemon you can interact with.
You should favor the management commands over the other commands if possible because the other commands really only exist for backwards compatibility.
You can get additional info on a command by running
docker [NAME-OF-COMMAND-HERE] --help.