Cancer immunity refers to the body's immune system's ability to recognize, attack and eliminate cancer cells. Under normal circumstances, the immune system is able to identify and destroy abnormal cells to prevent the occurrence of cancer. Cancer immunity involves the activities of immune cells such as T lymphocytes, B lymphocytes, and macrophages, as well as the regulation of immune regulatory molecules. Immunotherapy is a treatment that uses stimulating or boosting a patient's own immune system to fight cancer. A deep understanding of cancer immune mechanisms is crucial for developing innovative treatment strategies and improving survival rates of cancer patients.