Gingivitis is an infection that's an early sign of gum illness. It happens once plaque builds up between the teeth and gums.
Plaque is a layer that sticks to your teeth from food, germs and mucus. Over time this build up will result in infection of the gums.
The gums usually don't hurt with gingivitis, but treatment is very important.
Gingivitis is a lot of common in people that don't brush or floss their teeth usually. If it's not treated, the infection will happen again and may cause serious gum disease or tooth loss.