Helicobacter pylori are bacteria that attacks and infects the fine mucus lining of the stomach in humans.
The scientist agree that a wide array of ulcers (peptic) and some categories of gastritis are caused or originated by Helicobacter pylori infection. Yet, most people who are infected will in fact never know they had HP as they never develop or experience any symptoms.
HP lives in the human stomach only and is in fact the only known life form that can survive in such extremely acidic settign. HP is helix-shaped and that is the reason it was named helicobacter. HP can in fact screw itself deep into the belly lining to colonize it.