This is the root of the SaltStack configuration for Kubernetes. A high level overview for the Kubernetes SaltStack configuration can be found in the docs tree.
This SaltStack configuration currently applies to default
configurations for Debian-on-GCE, Fedora-on-Vagrant, Ubuntu-on-AWS and
Ubuntu-on-Azure. (That doesn't mean it can't be made to apply to an
arbitrary configuration, but those are only the in-tree OS/IaaS
combinations supported today.) As you peruse the configuration, these
are shorthanded as
the documentation in this tree uses this same shorthand for convenience.