Q. How different are the concepts of action potential, resting potential and excitation threshold concerning neurons?

Action potential is the maximum positive voltage level achieved by the neuron in the process of neuronal activation around + 35 mV the action potential triggers the depolarization of the neighboring regions of the plasma membrane and therefore the propagation of the impulse along the neuron.

Resting potential is the membrane voltage when the cell is not excited about -70 mV.

Excitation threshold is the voltage level about -50 mV that is the initial depolarization must reach for the action potential to be attained.