Apoptosis

The word Apoptosis comes from Greek: Apo meaning "Away" and Ptosis meaning "Falling".

Literally meaning "Falling Away", which is a type of cell death.
Apoptosis is one of the ways cells die.

One way is Necrosis, a type of death where the cell will swell and explode. This isn't an ideal cell death as when it "explodes" it can damage other cells around it and can cause cells from the immune system that cause inflammation as the immune system cells might believe that those parts from the cell that recently died from necrosis are invading the body and attacking it.
The human body tries its best to avoid necrosis as it usually happens when the body is exposed to a chemical toxin and it causes the cell to die unnaturally.

The other way is Apoptosis which is the less extreme way of cells dying, for example when your hands are forming in your mother's womb, your hand starts out in a sort of paddle, and Apoptosis widdles it down to form your fingers.
Apoptosis is kinda like dissolving the cells.

Another place where Apoptosis shows up is in a tadpole, when a tadpole turns into a frog, the cells use Apoptosis to remove the tail. 

Apoptosis is happening all the time in your body. It is meant to keep the cells from multiplying too much, while not damaging the cells around it. As too many cells can cause cancer.

Also when cells suffer from DNA damage, if they can't fix it by themselves, they undergo Apoptosis. So with Apoptosis, it can save you from cancer. 

Keep in mind that not all cells will die to Apoptosis. Some will die to Necrosis