Balancing chemical equations serves two major purposes. One is to balance out the total number of each type of atom on both sides of the equation. Since matter (atoms) is neither created or destroyed it is essential to account for each atom of the reactants and exactly where it ends up in the products. The second purpose is to conserve the total electric charge on both sides of the equation. If both the reactants and products are neutral (no net charge) then this is easy since any charges must add to zero. It there is a net positive charge on one side of the equation then there must also be a positive charge on the other as well. The reason is that since charged particles are also matter, they cannot be created or destroyed as well, so they must be equal on both sides of the equation.
so that way you can make sure that the chemicals that are together balnce equally then you balance the whole thing out.