pH and pOH are quantitative ways to express solutions of
acids and bases. The pH scale is a more convenient way than using exponential
notation for expressing concentration of hydrogen ions.

In general, for any hydrogen ion concentration of

1 x 10^{-n} moles/liter
= [H^{+}]

the pH is equal to

pH = n

Here is how it works mathematically.

The pH Scale

In general, for any hydroxide ion concentration of

1 x 10^{-n} moles/liter
= [OH-]

the pOH is equal to

pOH = n

When
the solution's pH is added to its pOH, the result is always equal to 14.