Gingivitis
Bleeding, red, or swollen gums are common signs of gingivitis, an early gum inflammation that can improve with plaque control.
[1][2]The short answer
Gingivitis is inflammation of the gums, usually caused by plaque collecting around the teeth.
[1]
What the change looks like

What does gingivitis look and feel like?
What causes gingivitis?
Can gingivitis turn into periodontitis?
Gingivitis affects the gums and is the early form of gum disease. If inflammation persists, disease can progress to periodontitis, where pockets form and the tissues and bone supporting the teeth can be damaged.
[1]What makes gingivitis more likely?
How is gingivitis diagnosed?
A gum examination looks for redness, swelling, bleeding, and changes in the gum margin. Checking the depth around teeth helps distinguish inflammation limited to the gums from deeper periodontal disease.
[1]How is gingivitis treated?
What affects gingivitis treatment cost in Dubai?
What happens when gingivitis continues?
Persistent gum inflammation can progress beyond gingivitis to periodontitis. At that stage, pockets, attachment damage, bone loss, loose teeth, and eventual tooth loss can develop.
[1]