Security Studies cover the security of referent objects, individuals, or states. Since the Second World War, the importance and depth of Security Studies have increased. In the post-cold war period, it was seen as a purely military field and was handled within the scope of the power policies of the states. In the post-Cold War period, it emerged as a multidimensional form. This research describes prominent approaches such as Realism, Liberalism, Peace, and Critical Security Studies and the most recent essential theories. The research underlines the three pillars of The Copenhagen School, which has contributed to the academic literature on securitization/desecuritization theory, regional security complex theory, and sectoral security approach in international security studies. In the securitization theory, any subject can be non-politicised, politicised, or elevated to a national security concern level. According to the Regional Security Complex pillar, standard points, security priorities, and security dynamics must coincide with establishing a region in the security realm. Lastly, the safety of human societies is affected by factors in five primary areas - military, political, economic, social, and environmental factors. The study concludes that the Copenhagen School occupies a significant position among security studies methodologies and offers a helpful framework for examining contemporary global security concerns.