The method of representing a chemical reaction with the help of symbols and formulas of the substances involved in it known as a chemical equation.
Chemical equations are of two types.
1. Balanced chemical equation= a balanced chemical equation has an equal number of atoms of different elements in the reactants and products.
CaCO3+ 2HCl CaCl2+ H2O+ CO2
2. Unbalanced chemical equation= an unbalanced chemical equation has an unequal number of atoms of one or more elements in the reactants and products.
CaCO3+ HCl CaCl2+ H2O+CO2

We balance equation to prove law of conservation of mass i.e matter neither be created nor be destroyed. 

Balancing equation= The process of making the number of different types of atoms equal on both the sides of an equation is called balancing of equation.