How do I turn off my video?

To hide your video without muting your microphone, press the V key or click the camera button on the self-view in the upper right corner of the screen.

How do I turn off my audio and video at the same time? 

Simultaneously mute your audio and turn off your video by pressing the Z key. That’s Sleep Mode. Your microphone and camera will be off, but you can still hear other users if they are in the same sound zone as you. You can’t see other users when you’re in Sleep Mode, though. 

Note: When someone else is in Sleep Mode, they can still hear you.