The potential of an individual electrode cannot be determined experimentally. The relative values ​​of the electrode potential are found by combining this electrode with a standard hydrogen electrode, which is the generally accepted international standard. The potential of a hydrogen electrode is taken to be zero at all temperatures, therefore, the potential of a given electrode is, in essence, the EMF of an element consisting of a given and a standard hydrogen electrode.

Structurally, a standard hydrogen electrode is a platinized platinum plate washed with gaseous hydrogen at a pressure of 1.013.105 Pa (1 atm) and immersed in an acid solution with the activity of H + ions equal to unity. During the operation of the hydrogen electrode, the reaction proceeds

H2 (g) = 2H + + 2e-

In practical work, instead of a fragile and often capricious hydrogen electrode, special, more convenient stable reference electrodes are used, for example Ag+/Ag, the potential of which with respect to a standard hydrogen electrode is precisely known 0.8B.

Dear Umay Amara thank you for your technical question. The term "standard electrode potential" can be easily checked n the general internet. For example, the respective Wikipedia entry already provides a goo overview:

https://en.wikipedia.org/wiki/Standard_electrode_potential

Please also have a look at the following instructive link:

6.2: Standard Electrode Potentials

https://chem.libretexts.org/Courses/Mount_Royal_University/Chem_1202/Unit_6%3A_Electrochemistry/6.2%3A_Standard_Electrode_Potentials

Moreover, there are various helpful YouTube videos on this topic available, e.g.

19.1 Standard electrode potential (HL)

https://www.youtube.com/watch?v=pORJQyP-2j8

Thank you for your answers.