How to use printf and why we use printf?

Today we learn about printf , so first of all we have to know that is printf? printf is a function in c programming, which we use to see output of a programming . 

#include<stdio.h>

int main()

{

   printf("star coder BD");

   return 0;

}

we know this code output is star coder BD, if we don't use scanf() function we can't get this out put