Abstract: Cytokine storm (CS) is an inflammatory response involving the whole body and has a variety of causes. CS-associated diseases include cytokine storm syndrome (CSS) and cytokine release syndrome (CRS). CSS involves infections and autoimmune diseases, and CRS is related to the adverse reactions of tumor immunotherapy. The understanding of CSS and CRS is incomplete. The two concepts are easily confused, especially in terms of treatment that extensively involves tumor immune checkpoint inhibitors and immune cell therapy. CRS is becoming increasingly common in clinical practice. Therefore, the correct diagnosis and understanding of CSS and CRS are crucial aspects in clinical and basic research. This review discusses the development history, classification, and mechanism of CSS and CRS. The aim is to aid the diagnosis, differential diagnosis, prevention, and treatment of CSS and CRS.