What is the meaning of ‘!’ In math and how do I use it?

In math, the '!' sign are used in factorial. Factorial is multiplications on numbers itself and with another numbers that less than the number itself. Example :

5! =5x4x3x2x1 or nx(n-1)x(n-2)...2x1

d. no, life is hard people go through stuff. i've also been through a lot recently, i know new bad situations are thrown at people everyday but at the end there's always things which makes life worth it.