A hernia is a part of an organ that moves out of its normal position to remain elsewhere in the body. A hernia can protrude from a natural cavity, or one that has been forced. In general, a hernia is caused by a weakening of the surrounding tissue that can no longer withstand the pressure exerted by the organ. The majority of hernias are localized in the abdominal or vertebral regions. A hernia is not necessarily painful. It can be treated surgically, by putting the organ back into its correct position and reinforcing the membrane enveloping it.