What's the Use of '\r' escape sequence?

I have C code like this:

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

I have used the \r escape sequence as an experiment. When I run the code I get the output as:

o world

Why is that, and what is the use of \r exactly?

If I run the same code in an online compiler I get the output as:

Hey this is my first hello world

Why did the online compiler produce different output, ignoring the \r?