Numerous water quality measures (WQM) have been identified and utilized to maintain water quality at the world level. Interestingly, no particular WQM is the perfect one for water quality for mankind’s usage. Importantly, the composite water quantifies index (CEQI) is required to summarize water quality conditions across global. Nevertheless, the water quality index (WQI) is adopted by many countries to maintain water quality. It is a prominent way to assess water quality in specific areas. In this book chapter, we have explained the diverse aspects of the importance of water and water quality. The fundamental concept behind the WQM and CEQI has also been explained on the basis of current literature to maintain researchers’ interest in this enormously significant field.