The formula H2O is commonly known as water. Water is a vital substance for all forms of life on Earth, comprising about 60% of the human body and playing crucial roles in various biological processes. It exists in three states: liquid, solid (ice), and gas (water vapor). Its unique properties, such as high heat capacity, solvent abilities, and cohesive forces, are essential for environmental and biological systems. Water not only sustains life but also shapes our planet by impacting weather patterns, forming rivers and lakes, and participating in the water cycle.