Regarding Standard Electrode Potentials

If the standard hydrogen electrode (SHE) is set arbitrarily to have a potential that is equal to 0 V, and has an absolute real potential. Then, in electrochemistry, how are the electrode potentials of other electrodes are determined using it?


Our high school textbook states that we form a galvanic cell from the SHE and another half cell of the electrode that we want to determine its potential. Then using the voltmeter, the voltage of the cell should resemble the standard electrode potential of the electrode. 


I really don’t get it, because the voltage should resemble the difference in potential between the electrodes.


