The phenomenon of the refugee crisis, which in recent years has gained uncontrolled dimensions, has also affected Greece to a great extent, mainly because of its geographical location as the south-east “gate” of the European Union. Thus, a large number of immigrants are in Greece, trying to join the community. From the period 2015-2016 onwards, large inflows of migrant populations were observed in Greece, which caused severe problems for local communities, which together with the relevant authorities were called upon to address the problems that arose with the management of the reception and accommodation (temporary or permanent) of a continuously increasing number of migrants and refugees. In this article, we analyze the definitions and categories related to migration and the refugee phenomenon. Then, we make a historical review of migration in Greece and the situation that prevails today. Finally, we describe the terms for vulnerable social groups, to which both refugees and migrants belong, as well as investigate the social exclusion that they experience.