Nerve impulses are electrical energy signals.
Human electrical energy is generated by chemical processes in nerve cells. An example of a chemical involved in the process is acetylcholine.
A nerve impulse is wave electrical activity that passes from one end of a nerve cell to another. Each impulse is the same size. The frequency (impulse per second) is what carries the information about the intensity of a nerve signal.
Billions of nerve impulses travel throughout the human brain and nervous system.