Short answers, pulled from the story.
Hindustani is an Indo-Aryan language spoken in North India and Pakistan as the lingua franca of the region, and also by the Deccani-speaking community in South India. It is a pluricentric language with two standard registers, Hindi and Urdu, so it is also called Hindi-Urdu.
Hindi and Urdu share the same grammar and core Prakritic vocabulary but differ in literary and formal words. Literary Hindi draws heavily on Sanskrit and is written in Devanagari, while literary Urdu draws on Persian and Arabic and is written in the Nastaliq style of the Perso-Arabic script.
As of 2025, Hindi and Urdu together constitute the third-most-spoken language in the world after English and Mandarin, with 855 million native and second-language speakers according to Ethnologue. The total number of Hindustani speakers was reported to be over 300 million in 1995.
The name Urdu derives from the Persian Zabān-e Urdū, meaning 'language of the camp', rooted in the Chagatai word Ordū meaning 'camp', which is cognate with the English word horde. The name appeared around 1780 and is believed to have been coined by the poet Mashafi.
Mahatma Gandhi endorsed Hindustani as a unifying or fusion language that could cross communal and religious divisions across the subcontinent. It was not seen as associated with either the Hindu or Muslim communities, unlike Hindi and Urdu, and it was considered a simpler language for people to learn.
Hindustani itself holds no official recognition from the Indian or Pakistani governments today, having lost currency after partition. It is instead recognised through its standard forms, Hindi, declared the official language of the Union in India, and Urdu, the national language of Pakistan and one of India's officially recognised languages.