So, she sets her alarm to go off.

We use the expression, to go off, when we are talking about something that makes a large noise, for example, such as a bell or an alarm clock.

You can also have a gun; the gun can go off means the gun fires and makes a noise.

Well here, we are using this verb, to go off, when we are talking about an alarm clock.

So, her alarm goes off at 6:20 - 20 after 6:00 in the morning - but she hits "the snooze button to sleep another ten minutes."

The snooze button, "snooze," button, "button," is something on an alarm clock that allows you to sleep a little more, usually for five or ten minutes.

So, it will stop your alarm, and then five or ten minutes later the alarm will go off again.

So, that is called the snooze button. The verb to snooze means to sleep, so it allows you to sleep a little extra time.