FYI, there’s a little debate over this in the English language, but many would say that the proper demonyms are Afghan for the Pashtun ethnic group, and Afghanistani (or rarely Afghanese) for people from Afghanistan regardless of ethnicity.

Afghani is their currency.

I believe it comes from a discrepancy between the Persian and Pashto languages. Afghani being the correct term in Persian, and Afghan being the term in Pashto.

Afghani is pretty widely used in English, and even appears in some dictionaries, but many argue that it’s not correct.

So a person is an Afghan, they eat Afghan food, wear Afghan clothing, have Afghan customs, and their currency is the Afghan Afghani (in case some other country ever adopts a currency called the Afghani and you need to differentiate between them)