LaunchSlaves

RemoteMachine["remotehost", "oscommands"]

a host description for a computer named remotehost using the command oscommands for connection and using the default connection type defined for LaunchSlave

RemoteMachine["remotehost"]

host description for a computer named remotehost using the default command $RemoteCommand for connection

"remotehost"

simple host name; shortcut for RemoteMachine["remotehost"]

$RemoteCommand

the default oscommands to use

RemoteMachine["localhost"]

host description for the local machine

$mathkernel

the default command to start a local kernel

The command LaunchSlaves[list] takes a list of such host descriptions as an argument and tries to establish a connection to each of the hosts listed.

Finally, you can assign a list of host descriptions to the global variable $AvailableMachines and use LaunchSlaves[] without an argument, which will consult this variable.