What is a vortex of a water tornado?

A vortex generator is an aerodynamic surface, consisting of a small vane that creates a vortex. Some surfaces on an airplane can result in air flow separating from the surface or skin. A vortex generator creates a tip vortex which draws energetic, rapidly-moving air from outside the slow-moving boundary layer into contact with the aircraft skin. This keeps the flow close to the aircraft surfaces.

Vortex generators delay flow separation and aerodynamic stalling; they improve the effectiveness of control surfaces.

You may see vortex generators as a row of small vanes that are mounted in a row along a tail surface.