There are three main types of neuron: sensory, motor and relay.
These different types of neurons work together in a reflex action. A reflex action is an automatic (involuntary) and rapid response to a stimulus, which minimises any damage to the body from potentially harmful conditions, such as touching something hot. Reflex actions are therefore essential to the survival of many organisms.
A reflex action follows this general sequence and does not involve the conscious part of the brain. This is why the response is so fast.
The nerve pathway followed by a reflex action is called a reflex arc. For example, a simple reflex arc happens if we accidentally touch something hot.
Organisms are able to modify a reflex action and overcome it, but this uses the brain and has to be learnt. For example, keeping hold of a hot object requires a nerve impulse to be sent to the motor neuron of the reflex arc to interfere with the normal reflex action to drop the object.