This article oversees the figure of "Police" and "Police force" from a wide spectrum of disciplines that guides the reader to understand this institution beyond a simple etymological exercise. There is a clear evolution path of the institution from a simple "public order" concept to a newborn institution with new duties assigned by modern Criminal Law that suppress the classical vision of ius puniendi that is now a political category conducted not sanction but to prevent, protect and repress felonies, within, a wide range of functions that historically have been given to Police Force. Finally it provides an explanation and solution to the phenomenon in which police force functions have been attributed to the army, knowing, that the army's nature and functions are opposed, on these aspects, to those of police