I hope that you can clarify the difference between the kuffar and ahlul kitab, as I know that ahlul kitab are the Jews and the Christians and that these are kuffar, and so what is the difference betweetn the two.
All of them are kuffar and ahlul kitab, that is the Jews and Chritians are kuffar and they are the same as other (non Muslims) in this discription. However they differ with other kuffar on two issues:
First: There is with them a heavenly book but there is distortion in it. But this is what is attributted to them (ie the name Ahlul Kitab – people of the book)
Second: The Muslim can eat from the sacrifice of the Jews and the Christians and marry Jewish and Christian women and this is not allowed for the rest of the kuffar.
Shaykh Nasr Al Fahd