It's a way of eating where you
fast for about 16 hours of the day (except for like water and
coffee and things like that), and then get your full calorie
intake in during one 8 hour window.
So, for example, you might stop all food
intake after 8 pm, sleep, wake up the next morning, and, except for non-sugary drinks (pure water, organic
coffee, tea, etc), you continue the
fast until mid-day, or even that evening.