Security studies are an essential field in international relations, which has undergone many changes over the years. To understand these studies, it is important to clarify the key concepts.Security is often linked to crime, but it also covers a wide range of concerns related to the protection of individuals, groups and interests. Security can be defined as the state or feeling of being protected against threats, risks and dangers, whether objective or subjective. It is omnipresent in many fields, such as defense, diplomacy, criminology, the environment, health, food safety, law and civil liberties, the economy, business and information systems.Security studies have evolved over time, moving from a focus on military armaments and states to a broader approach that takes into account other aspects such as geography, economics and non-military power. Thinkers in this field are faced with new challenges, such as the nature of the threats to be met and how to ensure sustainable security.