Pain is defined as the painful experience of sensory, emotional, cognitive and social dimensions associated with tissue damage or potential tissue damage. Pain is also classified according to the course of the disease, and the classifications can be transformed into each other because of the treatment, and pain has its certain causes. Pain is divided into two categories according to its course: acute pain and chronic pain. Acute pain is short-lived and occurs after surgery, trauma or other illnesses, and it is a warning to the body to seek help. Chronic pain tends to occur over a long period of time and can also occur for no clear reason for more than 3 months. Although chronic pain may be a symptom of other diseases, it can also be a disease in itself, characterized by changes within the central nervous system. Acute pain can turn into chronic pain if left untreated or improperly treated. This occurs when changes occur in the nerves within the nervous system, which can make the body more sensitive to pain, even in the absence of external pain stimuli. For example, people can feel pain by touching their skin with a breeze or clothing, which is known as pain sensitization. The longer the pain lasts, the greater the risk that the body will become sensitive to pain and that the pain will become chronic. Therefore, timely and effective treatment of acute pain is essential to prevent the transition to chronic pain. Pain is a relatively common phenomenon and a relatively obvious sensation. It is important to identify the site of onset of pain and the cause of onset to give timely treatment.