Persian Language, also known as Farsi, is the most widely spoken member of the Iranian branch of the Indo-Iranian languages, a subfamily of the Indo-European languages. It is the language of Iran (formerly Persia) and is also widely spoken in Afghanistan and, in an archaic form, in Tajikistan and the Pamir Mountain region.
Persian is spoken today primarily in Iran and Afghanistan, but was historically a more widely understood language in an area ranging from the Middle East to India. Significant populations of speakers in other Persian Gulf countries (Bahrain, Iraq, Oman, People's Democratic Republic of Yemen, and the United Arab Emirates), as well as large communities in the USA.
Total numbers of speakers is high: over 40 million Farsi speakers (about 60% of Iran's population); over 14 million Dari Persian speakers in Afghanistan (50% of the population according to CIA World FactBook & Britannica); and about 2 million Dari Persian speakers in Pakistan.
In Afghanistan Farsi is spoken almost everywhere and over 50% of Afghanistan's total population speak Farsi or Dari. The map on the right should cover Herat and the nothern parts of Afghanistan where the majority of people speak Farsi. - Thank you, Laila Ahmadi
Three phases may be distinguished in the development of Iranian languages: Old, Middle, and Modern. Old Iranian is represented by Avestan and Old Persian. Avestan, probably spoken in the northeast of ancient Persia, is the language of the Avesta, the sacred scriptures of Zoroastrianism. Except for this scriptural use, Avestan died out centuries before the advent of Islam. Old Persian is recorded in the southwest in cuneiform inscriptions of the Persian kings of the Achaemenid dynasty (circa 550-330 BC), notably Darius I and Xerxes I. Old Persian and Avestan have close affinity with Sanskrit, and, like Sanskrit, Greek, and Latin, are highly inflected languages.