The numbers in front of each element or molecule are called coefficients. They indicate the relative number of atoms or molecules involved in a chemical reaction. For example, in the balanced chemical equation CH4 + 2O2 -> CO2 + 2H2O, the coefficients are 1 in front of CH4, 2 in front of O2, 1 in front of CO2, and 2 in front of H2O. This means that 1 molecule of methane (CH4) reacts with 2 molecules of oxygen (O2) to produce 1 molecule of carbon dioxide (CO2) and 2 molecules of water (H2O).