Cancer does not refer to a single condition but encompasses a group of diseases characterized by the abnormal growth and division of cells. The causes of cancer are multifactorial and can vary depending on the type of cancer. Generally, cancer arises from a combination of genetic mutations, environmental factors such as exposure to toxins and carcinogens like tobacco smoke or certain chemicals, lifestyle choices including poor diet, lack of physical activity, and excessive alcohol consumption, as well as certain infections and family history of cancer.