Chemotherapy means the use of chemicals (ie drugs) to treat a disease, but of course we most commonly use the word when we’re talking about treating cancer.
What makes cancer so difficult to treat is that cancer cells are just the cells of your own body that have gone wrong because of mutations. That means that it’s very difficult to find ways to kill cancer cells without killing normal cells, since they’re so similar. One of the key things about cancer cells is that they divide very rapidly, so that’s what most chemotherapeutic drugs target – they kill cells that are dividing fast. The problem with this is that there are also normal cells that divide fast – like the cells lining your gut, and your hair follicles, so these cells get killed too. That’s why chemotherapy makes people feel sick and makes their hair fall out.
Does that answer your question? If you wanted to know more about exactly how chemotherapeutic drugs kill the cells that are dividing fast, ask me again and I’ll try to give you a good answer!