The Docker client is responsible for everything that containers do. There are a Docker clients available for most common operating systems, including macOS, Windows, and most, if not all Linux distributions. The Docker client can either be on the same host as the daemon, or long-running program, or it can connect to a remote daemon. It also provides the CLI, or command line interface, to start, stop, build, and execute commands within containers.
The Docker client is mainly used for pulling images and running them on the host.