"Electromotive force is like gravitational force. Everyone are familiar with gravitational force where an object will just drop to the ground due to attraction of gravity. Electromotive force is similar to it where electrons are attracted to the positive terminal of the voltage source. Just imaging the positive terminal as our ground and electrons are our objects so when we drop the electrons, it will fall to the positive terminal. The motion of electrons then creates an electric current that moves in the opposite direction."

The page has some very clear diagrams.