What is chemotherapy?

I thought it was about time I asked a question I've been wondering for a while - “Why are you injecting me with such serious poison?”. I got the following answer which just about explained the whole thing to me: Chemotherapy works by killing cells (with poison) .  This kills all cells but  cancer cells grow faster so it kills them sooner.  Like lawn mowing taller grasses. Eventually once they’re gone, the chemo stops and normal cells can continue to grow. Hair and skin cells also grow fast so they’re collateral damage in the wholesale onslaught of cell killing.

There are a number of different drugs involved in chemo to try to offset the mass of killing of normal, non cancerous cells and to mitigate the effects of losing healthy cells.