When plaque (a soft film of bacteria) is left on the teeth and gums, the gums become irritated and inflamed. The dental term for inflammation of the gums is called gingivitis. Plaque is a soft and white film which should be regularly removed with your toothbrush and interdental aids on a daily basis.
However, if the soft white plaque is not removed, it will turn into a yellow harder substance, us dentists call calculus. This is more commonly known as tartar. Calculus can no longer be removed at home and will require professional removal. Any calculus build up is a sign that particular area of your mouth is not being cleaned throughly. Over time, poor oral hygiene will lead to the development of gum disease.
Many patients report they stopped cleaning that area because it was bleeding. This is the worst thing you could do. If an area of your mouth is bleeding, you need to brush this area more, and the bleeding will eventually subside. If it doesn't subside, please do seek professional advice.
A high quality oral care regime is absolutely critical to the prevention of gum disease and decay of your teeth. Regular examinations and cleaning with your dentist and hygienist, will ensure any areas you are missing can be spotted early and resolved before further issues develop.