What is the electromotive force?
The difference in electrical potential between two points (like the cathode and anode).
Let's consider a typical galvanic cell:
In this cell, electrons are pulled from zinc, the anode, to copper, the cathode.
The electromotive force is the difference in potential that pulled the electrons from the anode to the cathode.
Electromotive force is measured in volts, which is defined as joules per coulomb.