The article offers information on pain, its causes and different types. Pain is a subjective experience and varies in its quality, intensity and nature from person to person and within the same person as well. Five different categories of pain such as acute pain, sub-acute pain, recurrent pain, chronic pain and cancer pain are described. The four main processes in the production of a nociceptive painful sensation such as transduction, transmission, modulation and perception are included. Descartes stimulus-response model of pain and the Gate Control Theory of pain modulation are also explained. Successful treatment of pain can be achieved by understanding the complexity of the pain experience