Healthy gums – Healthy gums are firm and pink
Gingivitis – The early stage of periodontal disease – gums become red, swell, and bleed easily
Mild Periodontitis – The beginning on bone and tissue loss around the tooth
Moderate Periodontitis – More bone and tissue destruction
Severe Periodontitis – Extensive bone and tissue loss, teeth may become loose
Source: Delta Dental of Virginia Blog