Necrosis means death of tissues, cells, or an organ in the body. This happens when not enough blood is supplied to the tissue, whether from injury, radiation, or chemicals. Once necrosis occurs, it is not reversible.
When substantial areas of tissue die due to a lack of blood supply, the condition is called gangrene.
It is not a good thing...If you really want to be grossed out, put it in google and check out the pictures. It will put you off lunch.
Bluesman