The world is increasingly influenced by the processes of globalization and internationalization. The importance of internationalization has been recognized also within the area of higher education. Higher education systems today are largely shaped under the influence of internationalization. To recognize the effects of internationalization in higher education, i.e., changes in the structure and activities that characterize internationalization, it needs to be defined. The paper presents a theoretical framework that explains internationalization, more precisely, the different concepts of internationalization. The Bologna system of education and the education system in the Republic of Croatia, which has been harmonized with the Bologna system for the purpose of internationalization of higher education in the field of EHEA, have been presented. It has been shown that the European qualification framework is linked to the international classification standard ISCED, indicating that the international learning outcomes framework is set for greater internationalization of education. The global survey suggests that there is no single definition or strategy of internationalization among the institutions, but a certain number of concepts. The results of studies show that a great number of countries and institutions have a strategy of internationalization, which is crucial for the implementation of internationalization. Mobility has been shown to be the most important activity of internationalization, but in practice there is still insufficient number of students applying for mobility. Although internationalization of higher education does not have a unified definition, the process of operationalization and the creation of an internationalization strategy involving institution`s and government`s policy is what is needed for its understanding and quality implementation. On the other hand, reviewing studies show that quality internationalization involves the changes of the work of individuals participating in the education system, changes in the attitude of individuals to different cultures and different international environments, and changes within institutions that enable individuals to advance in the development of intercultural competence. Certainly, further monitoring and research is needed to gain the best image of internationalization of higher education in practice and to improve quality.