Why is it important for cell death programs to exist? How do they contribute to normal physiology and the prevention of disease? What are the characteristics of Necrotic and Apoptotic Cell Death Pathways?

Apoptosis is the topic

Why is it important for cell death programs to exist? How do they contribute to normal physiology and the prevention of disease? What are the characteristics of Necrotic and Apoptotic Cell Death Pathways?