What is a balanced chemical equation why should the chemical equation be balanced?

A balanced chemical equation is when both the products and the reactants are balanced, or have the same number of atoms on each side of the equation. For example:

2H20 --> 2H2 + O2

This means there are 2 water molecules as the reactants (before reaction) and 4 hydrogen and 2 oxygen atoms as the products (after reaction).

Technically the equation wouldn't work in real life if it weren't correctly balanced.