This paper deals with the question of how norms are to be conceived of in order to understand their role as guidelines for human action within various normative orders, particularly in the context of law on the one hand and conventional morality on the other. After some brief remarks on the history of the term “norm,” the author outlines the most significant general features of actually existing social norms, including legal and conventional norms, from which he arrives at two basic requirements on an appropriate conception of such norms: the actuality and the normativity requirements. On this basis, he enters into a critical discussion of Kelsen's highly influential view of norms, arguing that this view is doomed to failure. In the last part of the paper, the author scrutinizes the more promising “practice theory of norms” by H.L.A. Hart, which, in his view, also suffers from some shortcomings, but may be modified in a way that leads to a conception of social norms providing us with a plausible explication of their actual existence and their normative force.