Colour saturation refers to the intensity of the colours in your photographs. A highly saturated image will have bright and vivid colours, whereas a low saturation image will have more subdued colours.
A Little More Detail:
You can change colour saturation in your camera before you capture the shot, for example, by editing the Picture Style settings, or in post-production by using image editing software. Generally speaking, most people like to see images with a subtle boost in saturation, to help make the image ‘pop’.