Use this phrase when you want someone to do something for a short time, like one or two minutes:

Take a moment to look over the sheet I just passed out.

Take a moment to think back to the last time someone paid you a compliment. How did it feel?

A "moment" is a short length of time which can't be specifically measured. It's also used in other phrases like:

The doctor will be with you in just a moment.

Can I have everyone's attention for a moment?

Excuse me, we're taking up donations for the Haiti Relief Fund. Do you have a moment?