Gingivitis is a common and mild form of gum disease characterized by inflammation of the gums. It is typically caused by poor oral hygiene practices that allow plaque to accumulate along the gumline, leading to irritation and swelling. Symptoms of gingivitis may include redness, tenderness, and bleeding gums during brushing or flossing. Gingivitis can usually be reversed with proper oral hygiene measures, including regular brushing, flossing, and professional dental cleanings.