One IF function has one test and two possible outcomes, TRUE or FALSE. Nested IF functions, meaning one IF function inside of another, allows you to test multiple criteria and increases the number of possible outcomes.
Testing more than one condition If you need to test for more than one condition, then take one of several actions, depending on the result of the tests, you can nest multiple IF statements together in one formula. You’ll often hear this referred to as “nested IFs”.
The idea of nesting comes from embedding or “nesting” one IF function inside another
It is very useful functionally of excel as it saves tons of time and simplifies work