Angiogenesis refers to the formation of new blood vessels in the body. It is a normal process that is necessary for children to grow, for the uterine lining to grow each month in pre-menopausal women, and for wounds to heal.
Angiogenesis is of interest in cancer, because cancers require the formation of new blood vessels to grow and metastasize. Cancer cells secrete substances that stimulate angiogenesis, and hence growth of the cancer. Some of the newer treatments for cancer are aimed at inhibiting angiogenesis (angiogenesis inhibitors). An example of an angiogenesis inhibitor sometimes used in lung cancer treatment is bevacizumab (Avastin).
Angiogenesis inhibitors are in turn considered a form of targeted therapy. Targeted therapies are anti-cancer medications that are designed to "target" cancer cells more specifically, and, in general, have fewer side effects than traditional chemotherapy.