Two couples with different electrode potentials may be combined to build a cell, a device to physically separate the oxidation from the reduction so that when the electrons move from one process to the other they pass through the external circuitry to do work. In this way, electrical energy may be extracted from a redox reaction. WOW!
The couple which is most negative will be the negative pole of the cell...and will be driven into oxidation. The other will, therefore, be reduction and the positive pole. Properly combined, remembering to balance the electron count in each half equation, the redox equation represents the cell reaction too.
With the emf being positive [ E cell = E rhe - E lhe] means that the reaction, when first built, is NOT at equilibrium. What is holding it up is the fact that no current is flowing. Once the circuit is completed, the cell reaction gets under way, and moves towards equilbrium. Once the system reaches equilibrium, the cell voltage falls to ZERO. The cell reaction is over, and a new cell must be built.