The Hue and Saturation tool controls color. Change the hue changes the color balance (eg change from red to yellow). Change the saturation alters the color intensity. If Desaturate (remove all color) to be left with a monochrome (black and white) image.
Practical Tips Hue and Saturation Photo Editing :
Desaturate - There is a fast way to make a black and white image - the desaturate command. Colorize - For some wild effects try the colorize command. It will put a colour wash over the entire image.
