Spotting is a technique used by dancers to help them maintain orientation during spins. When spotting, the dancer will generally maintain a smooth spin with their body, but will pick a fixed spot that they attempt to maintain visual contact on; as they spin they will watch this spot for as long as possible, and when their spin takes it out of their visual field they will whip their head around quickly to see the spot over their other shoulder.
This provides two major benefits. One is that it keeps them oriented on the stage, as keeping track of the spot lets them know exactly how many spins they have made and make sure that they are not drifting off their mark. Perhaps more importantly, spotting keeps the dancer from getting too dizzy. This works because dizziness is caused by a mismatch in sensory information; your eyes tell you that you are moving fast, but as you spin the liquid in your inner ear also starts to spin, and its movement past the sensory cells becomes smooth and unidirectional. Spotting jerks the head and thus also jerks the liquid, causing the chaos in your visual field to match the chaos in your vestibular system.