The equation "2H2 + O2 → 2H2O" represents a chemical reaction where hydrogen gas (H2) reacts with oxygen gas (O2) to form water (H2O). In this reaction, two molecules of hydrogen combine with one molecule of oxygen to produce two molecules of water. This process is an example of a combustion reaction, which releases energy. This reaction is essential for various natural processes, including respiration in living organisms and the water cycle. The formation of water from hydrogen and oxygen is also a key reaction in fuel cells, which convert chemical energy into electrical energy efficiently.