A circuit is a list of exercises that you perform more than once. When you add a circuit you can give it a name just like you can for an exercise or a workout. In addition to that you need to specify how many times this circuit will be run (rounds). A good example of this is one a friend of mine does called “One Hour Cardio”. To enter this as a circuit you set the name and set the number of rounds to 12. Then you add one exercise called “Run” setting the timing to 4 minutes. Then add another exercise called “Walk” setting the timing to 1 minute. The total for both is 5 minutes. Five minutes done 12 times is 60 minutes or one hour. When the app runs this circuit it will announce “Run 4 minutes” and then do nothing but silently countdown the 4 minutes unless you added extra timing. When that time is up it will announce, “Walk 1 minute” and again be silent until the minute is up. It will repeat this 12 times. When the whole circuit is done, assuming there is no more to the workout, the app will announce “Finished”.