Short answers, pulled from the story.
Persian, also known by its endonym Farsi, is a Western Iranian language belonging to the Iranian branch of the Indo-Iranian subdivision of the Indo-European languages. It is the most widely spoken of the Southwestern Iranian languages and originated in the region of Fars in southwestern Iran.
There are approximately 130 million Persian speakers worldwide. It is spoken and used officially within Iran, Afghanistan, and Tajikistan in three mutually intelligible standard varieties, and natively in the Tajik variety by a significant population within Uzbekistan.
Persian, Dari, and Tajik are three mutually intelligible standard varieties of the same language. Iran's variety is officially called Persian, Afghanistan's has been officially named Dari since 1958, and Tajikistan's has been officially designated Tajik since the Soviet era. Iran and Afghanistan write it in the Persian alphabet derived from Arabic script, while Tajikistan uses the Tajik alphabet derived from Cyrillic.
The Academy of Persian Language and Literature has maintained that the endonym Farsi should be avoided in foreign languages, and that Persian is the appropriate English designation. It argues that Persian has the longer tradition in western languages and better expresses the language's role as a mark of cultural and national continuity.
Persian is divided into Old, Middle, and New (Modern) periods. Old Persian was used in the Achaemenid Empire from 550 to 330 BCE, Middle Persian was an official language of the Sasanian Empire from 224 to 651 CE, and New Persian literature was first recorded in the 9th century after the Muslim conquest of Persia. Persian is the only Iranian language for which close philological relationships between all three stages are established.
Persian was used officially as a language of bureaucracy even by non-native speakers such as the Ottomans in Anatolia, the Mughals in South Asia, and the Pashtuns in Afghanistan. It became the sole official language under the Mughal emperors and served as the official language of the Sultanate of Rum. New literary languages including Ottoman Turkish, Chagatai Turkic, Dobhashi Bengali, and Urdu were built on the Persian model as structural daughter languages.