Hindustani also known as Hindi-Urdu, is an Indo-Aryan language, primarily spoken in Northern India and Pakistan, and communities from those countries abroad. By some measurements, it's the 3rd most spoken language in the world. The variety spoken in India is referred to as Hindi. The variety spoken in Pakistan is often referred to as Urdu. As an Indo-European language, it is (distantly) related to most European languages, and as such, a lot of its core grammar and phonology is vaguely recognisable to people that speak at least one European language.
Usually, the Devanagari Script is used in India and a variety of the Arabic script, called Nastaliq in Pakistan. Both communities use the Latin alphabet as well, especially online.
Hindustani has quite a few resources, most of these teach Hindi, with a minority offering Urdu as well
|Resource||Assimil||Pimsleur||Michel Thomas||Language transfer||Rosetta stone||Babadum|
|Available||Yes*(Only from French)||Yes*||Yes**||No||Yes*||No|
* As Hindi
** Community-made courses available as Hindi and Urdu
Learning Hindi- A site with a lot of info on Hindi, and a bit of info about Urdu which unfortunately appears to have been abandoned
https://hindilanguage.info/ - Another (unfortunately mostly abandoned) site with a lot of information about Hindi