One would note that the topic / title has the phrase "Indian Music" qualified within parenthesis with the other common terms like 'classical' , 'bhajan' , ghazal, 'geet' etc and even 'Bollywood'.
The reason being Indian music is a super set of all these different forms. Much like the country of India actually encompasses many different languages, peoples and cultures. It is similar to saying European music or if Europe was defined as one country. There would be so many different cultures and varied forms within that.
In any case, I guess you got the point about 'Indian Music'. If you are from India or that region it would be easier to comprehend the diversity within the overall form of music or the term used here i.e. Indian Music.
OK, here are some general definitions and guidelines-
Bhajans- devotional songs primarily bases on Classical Music which in turn means based on Ragas.
Ghazals - poetry primarily in Urdu language which have been given melody and composed into songs again based on Classical music and Ragas
Geet - Simpler songs both in terms of lyrics and the tune or melody composition but more closer to the common person and sung from the heart rather than mind
Bollywood Music - Songs from the Film Industry where traditionally most films were musical type films
Indian ( Hindustani ) Classical Music Grammar
Music is music , the notes are the same in Indian or Western or any other. The way we represent them and the way we structure them is different in these different forms of Music Grammar i.e Western or Indian Hindustani or Indian Karnatic etc.
The notes are
Sa , Re , Ga , Ma , Pa , Dha , Ni , Sa ( upper )
in western music it corresponds to
Do , Re , Mi , Fa , So , La , Ti , Do ( upper )
if you play these notes on a keyboard and start from the Middle 'C' they would correspond to
C , D , E , F , G , A , B , C ( upper )
<<< to be continued >>>
[ as noted in my other blogs/notes - these are general thoughts on different subjects and I would be editing and adding content and modifying these notes with time. My blogging is not time based but rather topic based ]