They're audio guided workouts for MP3's or iPods (you can also put them on a CD if you like). Cardio Coach workouts are intended for any cardio machine as well as for outdoor walkers/runners, and iTrain has all kinds of workouts; cardio, strength, flexibility -- you name it. I use Cardio Coach for elliptical workouts and I LOVE them. They make the time fly by and you get a great workout!
I just purchased the going back to school set - think that's a good deal? What one is the best as I recall seeing people talk about a certain volume that was super hard. Appreciate your feedback!!