How do I associate a launchd 2 plist with its domain and service targets?

What exactly are these "domain" and "service targets" and how do I associate them with plists for use by launchd?

OS X 10.10 introduces a new launchctl API for managing LaunchDaemons and launching plists. Log messages and man pages suggest that keys like KeepAlive and RunAtLoad should no longer be used and that subcommands enable; bootstrap; and kickstart should be used in preference to load -w and unload -w

However it is not clear from the man pages how to associate a plist with the "domain" and "service target" it talks about and without which these commands cannot be used with existing plists that seemingly were quite sufficient for OS X 10.9