The executor – not meant to be used directly by the user – is a CLI that launches a pipeline from within a job's Docker container (a.k.a. an Apache Beam's "driver").
Many commands from the klio-cli directly wrap to commands in the executor: a klio-cli command will set up the Docker context needed to correctly run the pipeline via the associated command with klio-exec.
The Docker context includes mounting the job directory, sets up environment variables, mounting credentials, etc.
As the klio-exec package is not meant to be installed directly, check out the installation guide for how to setup installation.
There is also the user guide and the API documentation for more information.