What does the mean H2O2

Hydrogen Peroxide

Explanation:

Hydrogen peroxide is a chemical compound with the formula H₂O₂. In its pure form, it is a very pale blue, clear liquid, slightly more viscous than water. Hydrogen peroxide is the simplest peroxide. It is used as an oxidizer, bleaching agent, and antiseptic. Concentrated hydrogen peroxide, or "high-test peroxide", is a reactive oxygen species and has been used as a propellant in rocketry. Its chemistry is dominated by the nature of its unstable peroxide bond.