Having an understanding of the properties of cytokines is essential for the immunologist, the researcher and the medical practitioner who need to understand immunologic diseases and immunological therapeutic approaches. Cytokines are redundant in their actions on target cells and promiscuous in their receptor reactions. (ED note: That is some cool use of English!) Moreover, many cells concomitantly produce several cytokines that have overlapping actions. Here this review provides conceptual framework to understand the intriguing aspects of the cytokine system.