To tell u the truth , 'Hindu' is not a faith, Its a label that refers to a race of people and their customs,
or rather, how people on the other side of Indus referred to those who dwelled
here (on this is side of Indus and around ).
The term seemed to have been coined by the Arab muslims as the first written reference of it is found in Ibn Battuta's works
and must have been a sort of blanket term for the people, their myriad customs and beliefs.
Over time just as the term 'Arab' and 'Muslim' have almost become synonymous to a large portion of non muslim world,
similarly the ethno and the religous aspects of the term, "Hindu" seem to have amalgamated over time
Ethinicity wise the demarcation of people who can be labelled as Hindus can be simply done by DNA
mapping and would also include a large portion of Indian Muslims
Faith wise it doesnt really refer to any one single way,
For the early muslims observers all that was practiced here on this side of Indus was Hinduism
While a lot of it is thought to be of as pure paganism by practioners of other abrahamic faiths,
It's infact a collection of beliefs, customs arts and even sciences among which some of them tend towards Polytheism
and some towards Monotheism, and some are what can be referred to just as Esocteric and Meditational sciences.
A lot of practising hindus often dislike being reffered to as Hindus and rather like to refer to their faith as "Sanatan Dharma" or the Eternal way
when one looks at the "Sanatana Dharma" texts closely its not so hard to wonder if it might have been even an early version of 'Islam' (Quite obviously it would not have an Arabic name), Interestingly and Coincidentlally the Hindu symbol for Om
and
Arabic Symbol for Allah
bear striking similarlity , especially if one turns them at right angle.
Its not hard to imagine that in the zeal to keep their faith pure
Muslims have largely avoided contact with anything so deeply Indian as Sanskrit and therefore consider all texts
written therein as Anti-Islamic.
for example the Prophet known as Noah (A.S) in the Books of Abramic Faith , seems almost like the semi-mythical figure "Manu" who gave the code that even today gives the dilapidated foundation to a lot of 'Hindu' practices,and is known as Manusmriti.
I can actually write an essay on this one, and i probably will sometime on some blog.
but i hope this answers your question for now .