Hello jibin,
You have THREE separate threads on NFC now.
Each of them have links that you obviously have not read.
YOU really need to study the subject and not just COPY what the kind members here tell you.
I don't understand why you chose NFC for your seminar speech if you know ZERO about it.
Go to your first and second thread and read the links properly. All the questions you ask are ANSWERED plus lots more.
Martin