Since an axon can be unmyelinated or myelinated, the action potential has two methods to travel down the axon.  These methods are referred to as continuous conduction for unmyelinated axons, and saltatory conduction for myelinated axons. Saltatory conduction is defined as an action potential moving in discrete jumps down a myelinated axon.
This process is outlined as the charge passively spreading to the next node of Ranvier to depolarize it to threshold which will then trigger an action potential in this region which will then passively spread to the next node and so on.
Saltatory conduction provides one advantage over conduction that occurs along an axon without myelin sheaths. This is that the increased speed afforded by this mode of conduction assures faster interaction between neurons. On the other hand, depending on the average firing rate of the neuron, calculations show that the energetic cost of maintaining the resting potential of oligodendrocytes can outweigh the energy savings of action potentials. So, axon myelination does not necessarily save energy.