In color photography the word saturation refers to the the intensity of colors. Saturation has a major effect on the look of photographs, and we react differently to different levels of saturation.
More sophisticated digital cameras provide a means of setting the saturation level in JPEG files in the camera.
As a pro I shoot RAW files, that is, digital files as taken and with no processing done by the camera. Most pros do that as it affords us maximum control over the images we shoot. RAW file record scenes as they look which has to be altered later if the photographer chooses to do so. For JPEG shooters who do post capture processing you ought to keep saturation set to normal in the camera and adjust it to your liking in post processing.
Most good photo processing software programs provide a means of altering saturation. I am a MAC user and have Apple's Aperture and iPhoto in my computer. Aperture is like iPhoto on steroids. It is professional strength and has more features than iPhoto, but iPhoto or a similar program like Photoshop Elements is all the average amateur photographer needs for most processing. Aperture allows me to adjust the saturation of all the colors with one setting or to adjust selected colors only. I photo allows only the saturation adjustment of all the colors.
In the gallery you will see five photos of the same scene of 20th Street and Tenth Ave. taken from the High Line walkway in New York City. The level of color saturation decreases in each photo with the first photo being the most saturated. The third photo is the image as it was produced in the camera as a RAW file. The last three photographs in the gallery show the effect of altering color saturation of a single color. You will surely see how saturation affects a color photo.