Afghan (Pashto/Persian: افغان; see etymology) refers to a citizen of Afghanistan. Prior to this definition, it was used by Persian speakers (and others influenced by Persian) to denote the Pashtun people. Nowadays, "Afghan" is usually not used as an ethnic term, but as a national demonym for all citizens of Afghanistan, while "Pashtun" - the native ethnonym of this people - is largely used in a linguistic sense to refer to native speakers of Pashto.
According to Encyclopaedia Iranica, the word Afghan (afḡān) in current political usage means any citizen of Afghanistan, whatever their ethnic, tribal, or religious affiliation is. According to the 1964 Constitution of Afghanistan, all Afghans are equal in rights and obligations before the law. The fourth article of the current Constitution of Afghanistan states that citizens of Afghanistan include Pashtuns, Tajiks, Hazara, Uzbek, Turkmen, Aymaq, Arab, Baluch, Pashayi, Nuristani, Qezelbash, Gujjars, Brahui, and others, who are native inhabitants of the country, and that all citizens of Afghanistan be called Afghans.
As an adjective, the word Afghan also means "of or relating to Afghanistan or its people, language, or culture".
Read more about Afghan: Afghani