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In contemporary terminology, people of Persian heritage native specifically to present-day Afghanistan, Tajikistan, and Uzbekistan are referred to as Tajiks, whereas those in the eastern Caucasus (primarily the present-day Republic of Azerbaijan), albeit heavily assimilated, are referred to as Tats. However, historically, the terms Tajik, Tat, and Persian were synonymous and were used interchangeably, and many of the most influential Persian figures hailed from outside Iran's present-day borders to the northeast in Central Asia and Afghanistan and to a lesser extent to the northwest in the Caucasus proper.In historical contexts, especially in English, "Persians" may be defined more loosely to cover all subjects of the ancient Persian polities, regardless of ethnic background.source:wikipedia