This article provides a general introduction for the so-called intelligence activities. Intelligence means the collection, analysis and dissemination of information needed by policy makers and decision takers. But it does not include all kinds of information or data in general, since intelligence is part of a conflict dealing with denial of knowledge and secrets. The unique methods, procedures, technologies and techniques of intelligence make it more relevant in some fields than others. National defense, foreign policy and law enforcement are the main users of intelligence. The article also addresses the tensions between intelligence and democracy and the expected impacts of the intelligence in peace and war.