Vinyasa litereally (and only) means movement. There are external movements of body and internal movements of breath and when linking these movements together (inhale up, exhale down etc.) the movements of concioueness may be harnessed. this facilitates the upward movement of the three bandha. Movement is a universal aspect of nature and occurs on many levels simultaneously
"O yogi, do not do asana (posture) without vinyasa"
The vinyasa in the traditional practice are variations on the theme of 'Suryanamaskara'. It is from this foundation that all other movements flow. The salute to the 'Sun' begins from samastithi (equal upright position). The practice of vinyasa means to come back to this equilibrium from each posture (or after the second side of a posture that has left or right) whether Standing, Sitting, Lying or Inverted. The equilibrium ofsamastithi implies both physical and mental balance.
Vinyasa flow yoga is a style of yoga that concentrates on a dynamic connecting postures that then create a flow between the more traditional poses. Through breath, the movement of the postures that are always done and are shared with special breathing called 'Ujjayi breathing' and the time of posture is held can be determined. The purpose of this style of yoga is to create heat within the body which then leads to sweating and ultimately purification of the body. Vinyasa flow can improve flexibility and strength with a reduced risk of injury
"Doing a shorter practice and doing it well (with awareness ) is far beneficial than doing a longer practice badly (with an over achieving mind-set)."