@ ram
A Standard Hydrogen Electrode (SHE) is an electrode that scientists use for reference on all half-cell potential reactions. The value of the standard electrode potential is zero, which forms the basis one needs to calculate cell potentials using different electrodes or different concentrations...
With the help of these we can measure any concentration value of oxidation and reduction potential by kjeeping one concentration as unity .
HOPE IT CLEARS YOUR DOUBT
ALL THE BEST .,.