We have all probably laid eyes on these little plates on the surface of the wings of an aircraft a couple times at least. So what do they do and how do they do that?
What is a Vortex Generator?
A Vortex Generator is a small tab/plate on the surface of the wing or other lift surface.

Vortex Generators on C208 Wing
What do Vortex Generators do ?
Vortex Generators are there to delay the separation of the boundary layer from the surface of the wing to increase our lift at higher angle of attacks.

Vortex Generators on C208 Horizontal Stabilizer
How do they do that?
As an object, wing or golf ball moves through the air it has a thin layer of air called the boundary layer. The boundary is slow moving, low energy and sticky and therefore as the wing or golf ball moves through the air the boundary layer falls behind and separates which causes a wake. This wake causes drag, slows the wing or golf ball down and decreases lift.
So, much like a golf ball with dimples, Vortex Generators create minor turbulence which gives the boundary layer more energy which helps it keep up with the wing or golf ball for longer. This delay in separation reduces the effect of the wake. This is especially helpful for wings at high angle of attack.

Vortex Generators on C208 Wing
I hope this simple explanation was helpful.
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