How do I log out of my MacBook Air?

Am a first time mac user using the latest MacBook Air. I have been trying to find out how to log out a user. No luck. The user guide says click Apple menu (helpfully showing the apple logo) and click Log out. But what the heck is an apple menu? There is no such key (with the apple logo on my MBA!!)

Or is shutting down the only way?!!!!!!

Am at my wits end.

thanks,

mano