why different types of ITR forms required?

in income tax rules there are five types of head 

every things comes under this 

itr are classified on nature of income 

like salary , business , income from non prifit organations 

also it is based what kind of busiess it is like company,firm ,AOP, BOI, etc

for all these thigs itr are different 

income tax is vast subject u need to 

clear ur basics first ( accounts , income tax )

work atleast for 1 year with tax consultant