In nature,we have different substances.Some are acidic,some are alkaline and others are neutral.In order to tell the nature of a given substance,Chemists use Indicators to determine the pH of the substance in question.The color shown by the indicator can be matched against a pH scale.

Another way in which the pH of a substance can be measured is by using a pH meter whose electrode is placed into the solution whose pH you want to measure and its read.