Diglossia

Hindi as a Diglossic Language Standard (Suddha) Hindi vs Hindustani:- Hindustani, commonly known as Hindi-Urdu and historically as Hindavi, Urdu, and, is the lingua franca of north india and Pakistan. It is an indo Aryan language and it is deriving primarily from the khariboli of Delhi, and borrows a large amount of vocabulary from Persian, Arabic, Sanskrit and Turkic. The colloquial languages are all but indistinguishable, and even though the official standards are nearly identical in grammar. They differ in literary conventions and in academic and technical vocabulary.
With Urdu retaining stronger Persian, Central Asian and Arabic influences, and Hindi relying more heavily on Sanskrit. Before the partisan of India, the terms Hindustani, Urdu, and Hindi were synonymous; all covered what would be called Urdu and Hindi today. The term Hindustani is still used for the colloquial language and lingua franca of North India and Pakistan, for example for the language of  bollywood films, as well as for several quite different  varieties of Hindi spoken outside the Subcontinent, such as Fiji Hindi and the Caribbean Hindustani of  Suriname and Trinidad.
Standard Hindi, the official language of India, is based on the khariboli dialect of the Delhi region and differs from Urdu in that it is usually written in the indigenous devnagari script of India and exhibits less Persian influence than Urdu. Many scholars today employ a Sanskritized form of Hindi developed primarily varansi, the Hindu holy city, which is based on the Eastern Hindi dialect of that region and thus a separate language from official Standard Hindi.

It has a literature of 500 years, with prose, poetry, religion & philosophy, under the Bahmani Kings and later on Khutab Shahi Adil Shahi etc. It is a living language, still prevalent all over the Deccan Plato. Note that the term “Hindustani” has generally fallen out of common usage in modern India, except to refer to a style of Indian Hindustani Classic Music. The term used to refer to the language is “Hindi”, regardless of the mix of Persian or Sanskrit words used by the speaker.
One could conceive of a wide spectrum of dialects, with the highly Persianized Urdu at one end of the spectrum and a heavily Sanskrit-based dialect, spoken in the region around Varansi, at the other end of the spectrum. In common usage in India, the term “Hindi” includes all these dialects except those at the Urdu end of the spectrum. Thus, the different meanings of the word “Hindi” include, among others: 1. standardized Hindi as taught in schools throughout India, 2. Formal or official Hindi advocated by Puushottam Das Tandon who was freedom fighter from Uttar Pradesh. e is widely remembered for his effort in achieving the official language of India status for Hindi and as instituted by the post-independence Indian government, heavily influenced by Sanskrit, 3. the vernacular dialects of Hindustani as spoken throughout India, 4. the neutralized form of the language used in popular television and films, or 5. The more formal neutralized form of the language used in broadcast and print news reports. Hindi has two forms: the H form called  Shuddha Hind and Hindustani Language.
Both are based on the same dialect that is Khariboli. The L variety, Hindustani (often simply called Hindi) contains many loanwords from Persian and Arabic (brought by the Arabic and Persian invaders in medieval times), along with a massive vocabulary of English loanwords which increase day by day. The L variety is identical with spoken Urdu—except for the fact that the latter is written in Perso Arabic script. The H variety was standardized in the 1960s during the movement to adopt Hindi as national language of Indian Union.
Shuddh means pure Hindi primarily uses words from Sanskrit to replace not only English loanwords, but also loanwords from Persian language and Arabic which had been nativized for centuries. These words are called Tatsama words, and they even replaced many tadbhav words, i. e. words with Sanskrit origin but having undergone profound phonological change. The L variety is used in common speech, TV serials and Bollywood movies and songs. The H variety is used in official and government writings, scholarly books and magazines, signboards, public announcements and public speaking.