Chroma adjustments affect the color of a video image, similar to the way luma affects the brightness. Changes to the color of the video aren't commonly required—in fact, some compression tools do not even include these filters.
Saturation controls the intensity of a color. Increasing saturation will have the effect of brightening a color artificially, while decreasing it (or desaturating) will remove the color, all without affecting the luminosity of the image.
Hue is the way of describing a color (for example, red or blue). The hue adjustment in compression tools shifts the color spectrum of the image. It is used to do simple color correction, most often when white levels or flesh tones do not appear correctly. This is a pretty coarse adjustment and should be used with care or not at all.