For an electrode in contact with an electrolyte solution having similar ionic nature, if the tendency of the electrode is to gain electrons and undergo reduction, the electrode is said to have a reduction potential.
Example, Ag electrode dipped in the AgCl electrolyte solution.
If the reduction potential is calculated under the standard condition of 1M electrolyte concentration, 298 K temperature, and 1 bar atmospheric pressure (if gas is involved), it is called standard reduction potential. The standard reduction potential is represented as Eored.
The standard reduction potential can be derived by using standard hydrogen electrode (SHE) as the reference electrode.