The main component of Vicodin is hydrocodone. It is similar to codeine and is a pain-killer which belongs to the group of narcotic analgesics.
Acetaminophen is a much weaker anesthetic. It helps to increase the effects of hydrocodone.
Hydrocodone and acetaminophen are intended for removing severe pain. There some other cases in which you can take Vicodin. For more information look through its indications.
Do not use this medicine if you are allergic to acetaminophen or hydrocodone, or other narcotic pain-killers such as fentanyl (Actiq, Duragesic), hydromorphone (Dilaudid, Palladone), methadone (Methadose, Dolophine), morphine (Kadian, MS Contin, Oramorph, and others), oxycodone (Oxycontin), and oxymorphone (Opana).