Hue-Saturation

I don't understand the hue & saturation sliders, also how does the colorize option relate to them.

Moving the Hue slider will change all colors in your image at once.
Adjusting the Saturation affects the intensity of those colors (negative numbers = more gray; positive numbers = more color saturation.)
If you click Colorize, you will be, uh... colorizing your image. Some people refer to this as tinting. Your image retains its values but all color information is under the control of the sliders. Select a color you like with Hue, and adjust its intensity with Saturation.