Working of fork() in linux gcc

fork() creates a new process and the child process starts to execute from the current state of the parent process.

This is the thing I know about fork() in Linux.

So, accordingly the following code:

int main() {
  printf("Hi");
  fork();
  return 0;
}

needs to print "Hi" only once as per the above.

But on executing the above in Linux, compiled with gcc, it prints "Hi" twice.

Can someone explain to me what is happening actually on using fork() and if I have understood the working of fork() properly?