Answer
The pH is the negative logarithm of the $H^+$ concentration:
$pH = -log[H^+]$.
The pH value is easier to represent, compared with the concentration in $M$.
Work Step by Step
The pH is easier to represent, because the logarithmic scale is capable of representing very small numbers by simple numbers, for example:
The concentration values between 1 and $10^{-14}$ $M$ can be represented by pH with values between 0 and 14.
