Pain is a feeling set off in the nervous system. Pain may be sharp or dull. It may come and go, or it may be constant. You may feel pain in one area of your body, such as your back, abdomen or chest or you may feel pain all over, such as when your muscles ache from the flu. Acute pain lets you know that you may be injured or have a problem you need to take care of.
Click here for more information. http://www.nlm.nih.gov/medlineplus/pain.html