Read the following passage and answer the given questions.

Dental health is an integral component of overall well-being, yet it remains one of the most neglected aspects of public health in developing nations. The World Health Organisation estimates that oral diseases affect nearly 3.5 billion people globally, with untreated dental caries—commonly known as tooth decay—being the most prevalent condition. In India, surveys indicate that over sixty per cent of school-age children exhibit signs of tooth decay, a figure that climbs even higher in rural and low-income communities where access to affordable dental care is severely restricted.

The roots of poor dental hygiene can be traced to multiple factors. Dietary habits play a critical role; the increasing consumption of refined sugars and carbonated beverages creates an environment in which bacteria thrive and erode tooth enamel. Inadequate brushing technique, infrequent dental check-ups, and a general lack of awareness about preventive care compound the problem. Fluoride deficiency in drinking water in certain regions further weakens enamel development in children, predisposing them to cavities at an early age.

Periodontal disease, which affects the gums and supporting structures of teeth, presents another serious concern. Left untreated, it progresses from mild gingivitis—characterised by swollen, bleeding gums—to severe periodontitis, which can result in tooth loss. Emerging research has established links between periodontal disease and systemic conditions such as diabetes, cardiovascular disease, and adverse pregnancy outcomes, underscoring the importance of oral health as a window to the body's overall condition.

Preventive dentistry, anchored in the simple practices of twice-daily brushing with fluoride toothpaste, daily flossing, and regular professional cleaning, can dramatically reduce the incidence of these conditions. Community-level interventions—school dental camps, mobile dental units in rural areas, and public awareness campaigns—have demonstrated measurable success in improving oral health indicators. Ultimately, bridging the knowledge gap and making affordable dental care accessible to all segments of society are the twin imperatives that health policy-makers must address.

What is 'gingivitis' as described in the passage?