It's an infection of the gums. It starts out as plaque, an opaque film on the teeth that hardens to form calculus or tartar. As tartar accumulates, it harbors bacteria which attacks the soft tissue around the gums. This early stage gum disease is called Gingivitis. Symptoms include red swollen gums, bleeding, bad breath and sometimes, an unpleasant taste in the mouth. Untreated, Gingivitis becomes Periodontitis. At this severe stage, bacteria destroys both the gums and the supporting bone structure. Pockets form where teeth are separated from the gums and surrounding bones. Left untreated, Periodontitis eventually results in tooth loss.