why we use exit() in c code example

Example: How to exit a c program

#include <stdlib.h>
#include <stdio.h>

int main()
{
	char choice;
  	choice = getchar();
  	if(choice=='Q') {
    	exit(0);    
    } else {
    	printf("Forget Code Retains");
    }

 	return 0;
}