Gum disease starts quietly. The first stage, gingivitis, often causes no pain, so people ignore it until it becomes more serious. Catching it early matters, because early gum disease can usually be reversed, while the later stages cause permanent damage to the bone that holds the teeth.
If you notice any of these, a professional clean and better home care may be all that is needed. Left alone, the inflammation moves deeper, pockets form between the tooth and gum, and the supporting bone slowly shrinks.
Brushing twice a day along the gum line, cleaning between the teeth daily, and not smoking are the foundations. A dentist or hygienist can remove hardened tartar that brushing cannot shift, and show you exactly where you are missing. Regular visits are what keep a mild problem from becoming an expensive one.