What is the pH value?

pH is the hydrogen ion concentration index, also known as "acid-base value."
Is a measure of hydrogen ion activity in solution, a measurement of the pH of a solution.

Usually, the water temperature is around 25°C. The solution is acidic when the pH is less than 7.
The solution is alkaline when the pH is greater than 7.
So when the pH is equal to 7, we call it neutral.