Yes, the
languages are Hindustani (Hindi and Urdu) and English, while the
scripts are Latin, Devanagari, and usually Nastaliq. Compare Russian (language) vs. Cyrillic (script). The use of the Latin alphabet to write languages that aren't traditionally written in it is called Romanization, and it exists for all sorts of reasons.
https://en.wikipedia.org/wiki/Hinglish says
> In India, Romanized Hindi is the dominant form of expression online. In an analysis of YouTube comments, Palakodety et al., identified that 52% of comments were in Romanized Hindi, 46% in English, and 1% in Devanagari Hindi.
The most common explanation for use of Romanization online between native speakers of a language that's traditionally written in some other script is limitations of computer systems. Those can include things like
* inconsistent character encoding support (different people or different software systems don't agree on which encoding to use, or some software system actually corrupts or filters out some encodings)
* poor input method support (it's hard to type in some other script on some devices)
* poor rendering support (some software system doesn't display some script well, e.g. failing to render ligatures between connected characters properly)
* legacy of historical software problems (people may have learned to use earlier systems that didn't have good language support, and may have developed workarounds that then persisted because of cultural inertia or individual habits)
* limited literacy (people might not have enough training and practice in a script to be fully comfortable reading and/or writing it, even if they're fluent speakers orally)
Almost every computer system supports ASCII perfectly, and so that can easily become a lowest common denominator for representing various languages. This is not uncommon online with Arabic and Chinese, in addition to Hindustani.
But I don't actually know the answer here; those are just some common trends related to representation of languages on computers...