Migrations as an inevitable fact of socioeconomic trends pose a security challenge for migrant countries, transition countries, and the countries where migrants come as to the ultimate destination. They are realized in a large area with a large number of participants and global consequences. This paper, through the basic determinants of migrations, statistical indicators on migrations, security challenges, risks and threats, migration policy and international security, provides answers to the questions about the numerical movement of migrants from the seventies of the last century to today on a global scale. Responses are also given about the reasons for triggering migrations, the most desirable migrant destinations, and the impact of migrations on security in departure, transit and destination countries. Particular attention is given to the last migration crisis that has largely affected the European Union.