Before stimulation, the electrical potential difference between the outside and inside of a nerve axon is known as

Concept: The electrical charge imbalance that exists between the inside of electrically excitable neurons (nerve cells) and their surroundings is known as resting potential. 

The difference in electrical potential between the outside and interior of a nerve fibre before excitation (polarized nerve fibre) is known as resting potential. It is around 70 mV.