As the name implies, receptors are structures that receive information. More specifically, receptors receive information about stimuli or physical changes in the internal or external environment. With receptors, our nervous system monitors various environmental conditions. Interoreceptors monitor internal body conditions whereas exteroreceptors monitor changes in the external environment.
More specific classification involves reference to the type of stimulus monitored by a receptor.
For example, your body has chemoreceptors, baroreceptors, photoreceptors, and tactile receptors. These monitor shifts in chemistry, blood pressure, light, and touch respectively. All receptors are linked to sensory neurons. Within the CNS, the stimulus is identified and if a response is required to maintain homeostasis, signals are sent to effectors along motor neurons. As an example of receptors we can look at the functions of two types of encapsulated tactile receptors, the Meissner's and Pacinian corpuscles in skin.