What is the use of power factor

Do you mean this:

2^2 ?

If so, this is used in numerous formulae you'll probably come across later on. It is also a shorter way to write the product of similar numbers.

Imagine writing

2x2x2x2x2x2x2x2x2x2x2x2x2x2

You can also write this like this:

2^{14}

Where 14 means that there are 14 twos to multiply

Use of power factor