Cancer is a term used for diseases in which abnormal cells divide without control and are able to invade other tissues. Cancer cells can spread to other parts of the body through the blood and lymph systems. There are over 100 different types of cancer, each classified by the type of cell initially affected. Cancer is caused by genetic mutations that result in uncontrolled cell growth. Risk factors include carcinogens like tobacco, radiation, and viruses, as well as genetic predispositions and age. Cancer diagnosis involves imaging scans and biopsies to detect tumors and stage the cancer. Prevention strategies aim to reduce exposure to risk factors through vaccination, controlling tobacco and alcohol use, healthy diets, and cancer screening programs.