I am bit confused between the role of project manager and business analyst. What is the basic difference between the two?
They're just different roles.
A PM is responsible for guiding the project to successful completion.
A Business Analyst is typically responsible for elaborating the solution from concept to detailed requirements.
There can be conflict between the two roles, also. In some organizations, there is a combined PM/BA role. I tend to recommend against them, because there is often a conflict of interests in how the project should be managed.
PM-oriented people tend to want to deliver the project on-time, on-budget, etc. BA-oriented people often tend to favor extending the project to improve the delivered product.