Many (Not all) neurons are myelinated by schwann cells. The myelination covers the neuron with a fatty layer with small gaps between each schwann cells. These small gaps are called nodes of ranvier. When an electrical impulse is triggered by hyperpolarisation and travels through the axon, these nodes of ranvier essentially allows the signal to jump between each nodes and drastically enhance its speed of conduction, this is the process of saltatory conduction. The process is essential in the peripheral nervous system where quick, automated responses are required (such as pain from touching a hot surface).