\r is the C-style escaped (backwhacked) character known as carriage return (correctly noted by mingux as being ASCII 0x0d = 13). On many terminals, this returns the cursor to the first cell of the current line. But this is by no means standard; there is no generally standard behaviour for \r and \n, especially not on hard copy terminals.

What C does guarantee is that whatever \r is, it will be a single character.