Gingivitis is the medical term for early gum disease or also called periodontal disease. 

Gum disease originates in the gums and are infections caused by bacteria and other materials left behind from eating or poor brushing.  Early signs of gum disease are chronic bad breath, tender or painful swollen gums, and bleeding after brushing or flossing.  These infections can eventually cause the gums to separate from the teeth, creating a deeper pocket for more debris to get trapped between the teeth and gums and further infection and decay.  If continued to go untreated, gum disease can lead to abscesses, bone loss, or periodontitis.

However, in many cases, gum disease is avoidable. 

Periodontitis is treated in a number of ways.  One method is through root planning which involves cleaning and scraping below the gum line to smooth the roots.  If effective, this procedure helps the gums reattach back onto the tooth.

Pregnancy has also been known to cause a form of gingivitis.  This has been linked to hormonal changes in the woman's body that promote plaque production.