Gum disease, also known as Periodontitis, occurs due to bacterial growth in the mouth and can lead to gum deterioration and loosening teeth. It usually starts out as gingivitis, with red and irritated gums, and progresses to a more serious, although fairly rare condition.
Periodontitis affects the area just below the gum line, between your teeth and gums, breaking down the tissue that holds your teeth in their sockets. Once this tissue has been destroyed, more and more bacteria accumulates leading to gum infection.
Plaque is the primary cause of gum disease. However, other factors can contribute to periodontal disease. These include:
Depending on the severity of the infection there are different treatment options that you’ll discuss with your dental professional.
Sources: https://www.webmd.com/oral-health/guide/gingivitis-periodontal-disease#1