In this study unsteady numerical simulations with software Star-CCM+ were conducted to understand clearly the Savonius wind turbine operation, especially by comparing static results (motionless wind turbine) and dynamic results (wind turbine in rotation). This study provides a new vision of its behavior. Indeed, the Savonius is so-called "drag" as its torque is maximum when the blades are perpendicular to the flow direction (maximum projected area). This fact is actually verfyed with a static study. However, the dynamic study shows that the maximum torque is obtained when the axis of the blade is parallel to the wind, so the Savonius wind turbine would be "lift". This study opens new perspectives for the optimization of the Savonius rotors.