What is the difference between a 0 Ohm Resistor and a piece of wire?
Zero-ohm resistors have several benefits over a simple bit of cable:


They can be used as a wire link and can be inserted automatically by PCB assembly robots. They come on a reel so no additional setup is required.
They can be used where a resistor may be or was used in certain design variations.
They can be used as test points.
They are often seen on single-sided PCBs to provide a jumper across some tracks to avoid impossible or very long alternate routes.


Wikipedia's Zero-ohm link has an interesting addition:


  The resistance is only approximately zero; only a maximum (typically 10–50 mΩ) is specified.[2] A percentage tolerance would not make sense, as it would be specified as a percentage of the ideal value of zero ohms (which would always be zero), so it is not specified.