Chemotherapy involves the use of drugs to kill rapidly dividing cancer cells. These drugs can be administered orally or intravenously and work by interfering with the cancer cells' ability to grow and divide. While effective, chemotherapy often affects normal cells that divide quickly, such as those in the hair follicles and gastrointestinal tract, leading to side effects. It is commonly used to treat widespread or metastatic cancer and can be used in combination with other modalities to enhance treatment outcomes.