This document discusses cancer, its classification and nomenclature. It describes the differences between benign and malignant tumors. Malignant tumors are named according to the tissues they arise from, such as carcinomas from epithelial tissue and sarcomas from connective tissue. Cancer stem cells are also discussed as an area of new research, as current chemotherapy does not target these cells which can self-renew and differentiate. Risk factors for cancer like viruses, bacteria, inflammation and the immune system are summarized.