There are two main kinds of balance, symmetrical and asymmetrical. Symmetrical means that everything is the same on either side of a dividing line (like a butterfly.) Asymmetrical is when things are not the same (when things do not qualify as symmetrical.) There are different ways to make things asymmetrical, such as shape, size, and color.
SYMMETRICAL BALANCE
This shows symmetry because there is a dividing line and everything on either side is a mirror image of the other side. ASYMMETRICAL BALANCE
This shows asymmetry with shape, size, and color. The much larger box throws off the balance as does the single circle. The different colors also make the balance not symmetrical. ASYMMETRICAL BALANCE
This is another example of asymmetry because of the sizing of the letters, as well at the changes in color. The different shapes of the letters makes it not symmetrical as well. 
