Set the policy for what to do to the Virtual Machine once it has been determined to be idle. The choices are to perform a Shutdown, a Shutdown and Revert or a Suspend. The shutdown action will attempt to perform a clean shutdown of the OS. The Shutdown and Revert option will perform a clean shutdown (which is needed in certain cases to ensure Hudson sees the slave go away) and will then restore the Virtual Machine to its last revert point. This revert point (called a snapshot in Lab Manager terminology) must be created outside of Hudson.
It is recommended to perform a Shutdown on the Virtual Machine rather than a Suspend. Suspend should only be used when it is not possible or is ill-advised to have the Virtual Machine be shutdown.