Undertaking a study on security issues, it is initially necessary to define the concept precisely, and to make it concrete. The term security, when used without any defining of its meaning, represents only a conceptual formation, which has no reference of existence in the material world. The aim of the article is to concretise this concept. To this purpose, it is necessary to indicate: to whom or what it may concern. In addition, in this article the author undertakes to indicate the perception of the situation for specific entities or objects with a possible insecurity or its opposite, i.e. safe situation. Possible threats caused by given subject, object and situation are also analysed.