What is a factorial and what is the purpose of it?

Step-by-step explanation:

Factorial is used to multiply any natural number with all the numbers smaller than it. It is denoted by n! (n is the natural number)

where n! = n * (n-1) * (n-2) * (n-3) * (n-4) so on ...

For example if we take factorial of 5.

Then,

5! = 5 * (5-1) * (5-2) * (5-3) * (5-4)

= 5*4*3*2*1

= 120

It is used for the questions which asks us to order a number of things or in how many ways you can arrange something ...