It's very useful for when we're trying to count how many different orders there are for things or how many different ways we can combine things. For example, how many different ways can we arrange n things? We have n choices for the first thing.

How are Factorials used in real life?

I understand that a factorial of n items gives you the number of ways you can arrange the given items. For example: If there are two coins - you can arrange them in two different ways - like wise if you have 3 coins - there are 6 ways you can arrange them.

How do you explain factorial?

Factorials are very simple things. They're just products, indicated by an exclamation mark. For instance, "four factorial" is written as "4!" and means 1×2×3×4 = 24. In general, n!