Intermittent fasting is an umbrella term for ways of eating that restrict calories (i.e., fasting) during a certain window of time. In addition to the 16:8 or Leangains diet and Warrior Diet, there are three other popular ways to intermittent fast: 5:2 or the Fast Diet; Eat, Stop, Eat; and Alternate-Day Fasting.
For the 5:2 diet, you fast for two days a week where you restrict your calories to 500 or fewer a day. On the other five days of the week, you can eat as you please. It's a diet that helped Jimmy Kimmel and Benedict Cumberbatch slim down.
On Eat, Stop, Eat, you fast for a full 24 hours once or twice a week. It's like the 5:2 diet but stricter, and not eating anything for 24 hours is difficult for most people. But like 5:2, you can eat whatever you want the other days of the week.
If you follow Alternate-Day Fasting, you fast one day, whether by not eating at all or eating 500 calories or fewer, then eat normally the next day, then repeat. Since you're fasting more frequently than you are on 5:2 or on Eat, Stop, Eat, it may be a hard method of eating to maintain.