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by lunarg on May 15th 2016, at 12:31
Control + Shift + Eject*Locks your Mac so you will have to unlock it with your password. Note that this will also sleep the display but the Mac will continue to run.
Command + Option + Eject*Puts the entire Mac asleep. This is the same as clicking on the Apple-icon at the left-top and choose "Sleep".

* Newer Macs: Eject = Power

To properly "lock" your Mac when using either of the shortcuts, you will have to enable Require password after sleep or screen saver begins (System Preferences → Security & Privacy). When not set to immediately, the configured delay will be used when using the shortcuts.