What does it mean to die of natural causes? what happens?

Usually unexplained: To die of natural causes usually implies that no artificial cause, accident, homicide, etc, or that no obvious disease process was the cause of death. Usually in this case, the deceased may have died at home or outside of the medical system and no other obvious cause is identified. Most likely death is due to a fatal abnormal heart rhythm.

Due to disease: Natural causes are due to normal aging process or diseases as opposed to violent deaths like a suicide or homicide( these are unnatural causes).

A term for lawyers: As a pathologist, i must certify manner of death as (1) homicide (someone did something to cause the death of another); (2) suicide (the person's willed self-destructive act set in motion the events leading to death); (3) accident (a mishap, rather than illness, set the fatal chain in motion); (4) natural (i.e., disease); (5) undetermined (i cannot tell).