Logout, Restart and Shutdown are all self explanatory to me.
What are the differences between Suspend and Hibernate on the shutdown menu?
Suspend does not turn off your computer. It puts the computer and all peripherals on a low power consumption mode. If the battery runs out or the computer turns off for some reason, the current session and unsaved changes will be lost.
Hibernate saves the state of your computer to the hard disk and completely powers off. When resuming, the saved state is restored to RAM.
The power-management scripts use these terms: