Programmed cell death (PCD) is referred to as apoptosis.
The cell death may be initiated by a specific stimulus or as a result of several signals/stimuli received from the external environment.
Apoptosis takes place as a result of inherent cellular mechanisms, which finally lead to self destruction of the cell.
A series of molecular events are activated by the cell which cause an orderly degradation of the cellular constituents having minimal impact on the neighbouring tissues.
Example: The formation of fingers and toes of the foetus requires the removal of tissues between them which is usually carried out by apoptosis.