The term “security” is a much broader one than it is thought because of its dept and width. In order to understand its whole coverage, the answers of the following questions should be observed. Whose security? What kind of security? It can also be asked like ‘What is the object and subject of security?’

According to the realist perspective, the major object of security is State, which they also consider it as the major actor in the international system. However there are also other actors in the system such as international organizations, multinational corporations (MNCs), and non-Governmental organizations (NCOs). In addition to the actors of the international system, a certain region or the globe in general can be included in the list of the objects of security.

The subject of security is divided into five major sectors: military, political, economic, societal, and environmental. Generally speaking, military security concerns the two-level interplay of the armed offensive and defensive capabilities of States, and States’ perceptions of each other’s intentions. Political security concerns the organizational stability of States, systems of government, and the ideologies that give them legitimacy. Economic security concerns access to the resources, finance and markets necessary to sustain acceptable levels of welfare and State power. Societal security concerns the sustainability, within acceptable conditions for evolution, of traditional patterns of language, culture and religious and national identity and custom. Environmental security concerns the maintenance of the local and the planetary biosphere as the assential support system on which all other human enterprizes depend. These five sectors do not operate in isolation from each other. Each defines a focal point within the security problematique, and a way of ordering priorities, but all are woven together in a strong web of linkages.