Today, in France, the term "health monitoring" is widely used. It encompasses, however, a range of concepts on which there is not always consensus. The same is true of the activities associated with it, even though some—such as surveillance—already have definitions accepted by all. The concepts of observation, vigilance, and alert, for example, have not always been clearly defined. Furthermore, the use of these terms in everyday language perpetuates this ambiguity. Therefore, we felt it necessary to recall these definitions where they existed in the literature or legislative texts and to make suggestions where they did not. This effort at formalization could not be successfully carried out without reflecting on the structure of health surveillance and its components. Here too, proposals are made, introducing the concepts of “preformatted” and “non-preformatted” surveillance: definitions, functions, and operational components (methods and tools, processes) of these two forms of health surveillance are proposed here, along with the cooperative relationships between them. The intention is to provide the scientific community with a reference framework for exchanging information derived from surveillance activities, as well as to promote research and methodological development dedicated to this application of epidemiology in public health.