The nervous system takes in information through our senses and processes the information and triggers reactions. A neuron has three main parts, the cell body directs all activities of the neuron. Billions of neurons work together to create a communication network. Different neurons have different jobs.
So then, how are messages transferred from neuron to neuron?
A neuron receives an electrical signal called an impulse. Impulses are passed from neuron to neuron until they reach their final destination. Messages in neurons travel through a myelin sheath in the axon which acts like an insulator for the electrical impulse to move smoothly down until it's ready to reach the next nerve cell in line. Nerves don't touch, so in between the axon terminals, there is a gap called a synapse. Any message that travels down the neuron needs to jump the gap using special chemicals called neurotransmitters.
For example, if you touch a hot plate, you reflexively pull back your hand and your nerves simultaneously send pain signals to your brain.
In short :
Receptors are groups of specialized cells. They detect a change in the environmental stimulus. In the nervous system, this leads to an electrical impulse being made in response to the stimulus. Sense organs contain groups of receptors that respond to specific stimuli.