Why is the factorial of 0, 1? Explain in a comprehensible way.

In math terms the! stands for factorial. The factorial of a number is the multiplication of all positive integers under that number for example the factorial of 0, 0! is 1 because when you factor the lowest possible factor that you can get is 1 therefore even though 0 is nothing the lowest possible is 1 therefore it has to be one. So now to factor 1, 1!=1 and that's it!=)