P90x is a workout that can be done by anyone at any fitness level. It is designed to get great results in 90 days, and it's proven to be successful time and time again.
P90x2 is a graduate program, meaning that you should complete at least one round of P90x before you do P90x2, although technically this isn't required. You could jump right into P90x2 if you wanted. P90x2 is designed to increase athletic performance, while sculpting and creating a nice body as a body product of the training.
P90x3 is similar to the original P90x, it is NOT a graduate program and can be done by anyone. Just like P90x, P90x3 is designed to get great results in 90 days.
One of the main differences between P90x and P90x3 is that the P90x3 workouts are only 30 minutes long, which is awesome!
