The deal is that you look at the gif of the spinning lady and the way you see her turning indicates whether you are using your left brain or your right brain (no, I don't know how scientific this actually is, but it's fun...)
If you see her turning clockwise, then you use more of the right side of the brain and vice versa. Most of us evidently see the dancer turning anti-clockwise though you can try to focus and change the direction.
I find that if I glance at text then look back at the picture, she'll be spinning anticlockwise (i.e. I'm using the left brain), then to get her to spin the other way, I glance at the photo on my desktop, and off she goes clockwise, exercising my right brain! Thinking of a maths problem versus thinking of drawing shapes has a similar effect. Kind of fun!!
According to the blurb that usually accompanies the picture, LEFT BRAIN FUNCTIONS are: uses logic, detail oriented, facts rule, words and language, present and past, maths and science, can comprehend, knowing, acknowledges, order/pattern perception, knows object name, reality based, forms strategies, practical, safe; and RIGHT BRAIN FUNCTIONS are: uses feeling, "big picture" oriented, imagination rules, symbols and images, present and future, philosophy & religion, can "get it" (i.e. meaning), believes, appreciates, spatial perception, knows object function, fantasy based, presents possibilities, impetuous, risk taking.