Dari is a dilect of Persian language, spoken in Afghanistan. It is the Language of majority of Afghanistan people, according to the CIA's factbook.
Dari is the official and the most common language spoken in Afghanistan.
CIA World Factbook are listed in the chart in the sidebar, below the map of languages by region. Persian (Dari dialects) 50% and Pashto 35%. Pashto and Persian are the official languages of the country. Hazaragi, spoken by the Hazara minority, is another dialect of Persian. Other languages spoken include Turkic languages (primarily Uzbek and Turkmen) 9%, as well as 30 minor languages 4% (primarily Balochi, Nuristani, Pashai, Brahui, Pamiri languages, Hindko, etc.). Bilingualism is common.
According to the Encyclopædia Iranica, the Persian language is the mother tongue of roughly one-third of Afghanistan's population, while it is also the most widely used language of the country, spoken by around 80% of the population. It further states that Pashto is spoken by around 50% of the population.
فارسی دری، زبان اکثریت مردم افغانستان است.
Translation: Dari (Farsi) is the language of majority of Afghanistan's people.
Pashto (also: Pakhto, Pushto, Pukhto, Pashtu, or Pushtu), is the language spoken by 35% of Afghansitan's people and almost 15% of Pakistanis. (Source: CIA World Factbook and Wikipedia). Pashto belongs to the Eastern Iranian branch of the Indo-Iranian language family.
زما ژبه، پختو دی
Translation: My language is Pashto.