A chemical equation is balanced, when there are the same amount of atoms in both sides of the equation. Here are some examples of non-balanced and balanced equations:
[tex]O_{4} + CO_{2} \neq O_{3} +CO_{2}[/tex] → non-balanced
[tex]H_{8} + C_{2} = 2H_{4} + C_{2}[/tex] → balanced
Hope it helped,
BioTeacher101