The rotor blades of a lift based wind turbine are shaped like airfoils, so the wind flowing around them creates a lift force which in turn moves them around. From a thermodynamic viewpoint and like answered in this question kinetic energy is extracted from the wind during this.
But what goes on from a mechanical perspective? How exactly is the kinetic energy of air particles transferred onto the rotor blades via lift? None of the sites I read gave an elaboration on the how.
The answer to this question is very much analogous to the answer to how aeroplanes fly. See Physics SE Question "What Really Allows Airplanes to Fly?" and the best (IMO) answer is this one here.
But basically the airfoils, sails or vanes - whatever they may be called - deflect the flow of air. They do this by pushing on the air and changing the latter's momentum state. By Newton's third law, therefore, the deflected air pushes on the sails, and, for a wind turbine the design is such that this reaction force exerts a torque on the system.
