H2O2 is commonly known as hydrogen peroxide. It is named hydrogen peroxide because it is composed of hydrogen, H, and a peroxide group, O2. Hydrogen peroxide decomposes into water, H2O and oxygen gas, O2, when it is heated.
Hydrogen peroxide is most commonly used in dilute concentrations of around 3 percent as a first aid antiseptic; it foams upon contact with blood, helping to physically clean a wound in addition to killing bacteria. However, hydrogen peroxide also has many other household uses. It works very well to remove bloodstains from clothing. Its bleaching action makes it a good tile scrub, and its antiseptic properties make it effective at controlling mold and mildew.