The main, and official language in Iran, and Afghanistan. (Persian Farsi, Afghan Farsi.) The Farsi in both countries are stlightly different. But if a true Persian and a true Afghan meet for the first time, they will understand each other. Basically it's like comparing the American English to the British English.
It is one of the oldest languages still in use today.
It is an ancient Indo-European language.
"Ha'al e shomah chetoreh"
If you want to say "How are you" in Afghan Farsi you'd say:
"Afha'al e shomah chetor"
Person 1: O bacha, chee gap ast?
Person 2: Cheezay nay. Tu chee go mekhori?!?!?!
Person 1: Khak da saret o padar lanat!!!