Hey there Joe!
The color wheel in kuler (and in Illustrator for that matter as well) use the HSV (also known as HSB) color model. Moving in a clockwise/counterclockwise direction adjusts the Hue value. Moving towards the center of the wheel or away from the center of the wheel adjusts the Saturation. Dragging the slider that appears beneath the wheel adjusts the Value (or Brightness).
The sliders that appear towards the bottom of the screen do allow you to derive simulated values in a variety of other color models and methods including CMYK, RGB, LAB, and Hexadecimal.