A hernia is a general term which refers to a protrusion of a tissue through a structure or part of an organ. In other words, when something penetrates through muscle tissue or a membrane and sticks out. A hernia has three parts - the hernia's contents, the hernia sac, and the orifice (the hole).

Hernias most commonly occur in the abdomen. A part of the abdominal wall may be weak and allows a localized hole to develop - this hole is also known as a defect. Tissue, or abdominal organs may stick out through this hole. A hernia that involves the spinal discs commonly causes pain in the lower back, the pain can radiate down one or both legs (sciatica).

Not all hernias cause pain. Some people may have a hernia and not be aware of it. In most cases, however patients with a hernia do feel some pain or discomfort, and typically sense a lump in the affected area. Fatty tissue will usually jut through first, then an organ may protrude later.

There are several different types of hernia:

Inguinal hernia is the most common. This happens occurs when part of your bowel squeezes through your lower abdomen into the groin.

Hiatus hernia is when part of your stomach pushes up into the chest through an opening in the diaphragm.

Femoral hernia happens when fatty tissue or a part of the bowel pushes through into the groin at the top of the inner thigh.

Incisional hernia is when tissue pushes through a surgical wound in the abdomen that has not completely healed.

Umbilical hernia is when fatty tissue or a part of the bowel pushes through the abdomen close to your belly button (navel).

Epigastric hernia is when fatty tissue pushes through your abdomen, between the belly button and breastbone (sternum).

Spigelian hernia is when part of your bowel pushes through your abdomen by the stomach muscle below the belly button.

Muscle hernia is when part of your muscle pushes through the abdomen sometimes after a sports injury.