Gingivitis is an inflammation or redness affecting the gums surrounding the teeth caused by bacteria accumulating on teeth, around under the gum line. It is in fact the early stages of gum disease.
A gingival pocket is a space between the gum and the root of the tooth. In a healthy tooth the gingival pocket is between one and two millimetres deep and does not bleed on gentle probing with a special blunt measuring tool. In early gingivitis the pocket enlarges to between two to three millimetres, is not usually tender and often bleeds when disturbed by cleaning or by probing. Signs of gum disease are usually bleeding when brushing or flossing teeth, redness, swelling and occasionally tenderness.
As gum disease progresses due to infrequent or ineffective oral hygiene, the gingival pocket gets deeper tracking down the root and destroys the bone around the tooth.