Vinyasa Flow Yoga is an offshoot of Ashtanga Yoga. Ashtanga literally means '8-limbed'. Here limbs include moral and ethical rules of living, physical workouts, breathing exercises, as well as meditation.
This is a sequence of flowing Yoga poses connected to the breath. The point is to purify and stretch your body and reinforce your physical resources while amassing life force energy. For this it is recommended that you have some earlier experience in Yoga.
The core of Vinyasa Flow Yoga practice comprises 6 increasingly difficult series of connected postures. All of them call for 90 minutes to 3 hours to finish. A practitioner is supposed to prove competence at one series as a precondition to proceeding to the next. The first two series are quite simple and easily available. Beyond third you will most certainly have to seek the assistance of a trained, qualified and experienced tutor.
In fact, just a couple of people have mastered all 6 sequences so far.
Basically, there are 4 fundamental definitions of Vinyasa:
Vinyasa is a powerful tool that has successfully been employed in a number of yoga forms above and beyond Vinyasa Flow. Ashtanga Yoga, Power Yoga, Jivamukti Yoga, Viniyoga, Universal Yoga and Iyengar Yoga all of them slip in Vinyasa into their styles. In fact, Jivamukti Yoga says that "The breath is the outer Vinyasa, or connecting element; the intention is the inner Vinyasa."
However, in all forms of Yoga by slipping in Vinyasa, you get a conscious awareness of moving your breath with your body.