The chemical equation describes the reactants and products involved in a reaction.

Here's a breakdown:

* Reactants: These are the substances that are present at the beginning of a chemical reaction. They are written on the left side of the chemical equation.

* Products: These are the substances that are formed as a result of the chemical reaction. They are written on the right side of the chemical equation.

For example, in the combustion of methane:

CH₄ + 2O₂ → CO₂ + 2H₂O

* Reactants: Methane (CH₄) and Oxygen (O₂)

* Products: Carbon dioxide (CO₂) and Water (H₂O)

The chemical equation also indicates the stoichiometry of the reaction, which means the relative amounts of each reactant and product involved. In this case, one molecule of methane reacts with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water.