The pH scale is the measure of acidity (concentration of H+ ions) or alkalinity (concentration of OH- ions) in a solution.
pH ranges from 1 to 14 and indicates whether a solution is acidic, neutral or alkaline.
Acidic solutions pH range from 1 to 7
Neutral solutions pH of 7
Alkaline solutions pH greater than 7
If a solution is too basic and one wants to lower the pH then a solution of an acid or an acid salt is added.
If a solution is too acidic, one can add a base/ a base salt to the solution increasing the pH.