* H₂O is the chemical formula for water. It contains two hydrogen atoms and one oxygen atom.

* H₂O₂ is the chemical formula for hydrogen peroxide. It contains two hydrogen atoms and two oxygen atoms.

The difference in the number of oxygen atoms makes these two compounds completely different in terms of their chemical properties, physical properties, and uses.

* Water is essential for life and is a common solvent.

* Hydrogen peroxide is a powerful oxidizer and is used as a disinfectant, bleach, and in rocket fuel.