Pain is defined as a localized physical suffering associated with bodily disorder that is characterized by discomfort and leads to evasive action. It is classified as either acute pain lasting less than 6 months following an injury or chronic pain lasting more than 6 months. Pain is modulated through transduction, transmission, and perception in the nervous system and influenced by psychological factors like anxiety, depression, and previous experiences. Treatment approaches include pharmacological interventions using analgesics, non-pharmacological methods like acupuncture, and surgical procedures in severe cases.