Specifies the method by which the Jenkins agent will be launched.
Java Web Start
Relies on processes within the virtual machine to connect to Jenkins. If you use this, you may find it useful to use GuestInfo Properties to pass data to the virtual machine telling it where to connect to.
Execution of command
The Jenkins master machine runs a command the connect to this agent.
SSH (default)
The Jenkins master logs into the agent via SSH, using the credentials specified, and uses that session to push the agent code onto the agent and then run it. You should leave the "host" field blank as the plugin will automatically fill that in itself (once it knows the IP address of the agent).