What s the Use of r escape sequence

Question

I have C code like this:

#include<stdio.h>
int main()
{
    printf("Hey this is my first hello world \r");
    return 0;
}

I conducted an experiment using the r escape sequence. 

I get the following output when I execute the code:

o world

Why is that, and what does r actually do?

If I use an online compiler to run the same code, I get the following results:

Hey this is my first hello world

Why did the online compiler ignore the \r and create different output?