What is the difference between Ilford's range of films?

Q. What are the differences between Ilford's range of films?

A.  Ilford have a good description of their types of film here 
http://www.ilfordphoto.com/aboutus/page.asp?n=29

It is important to note that XP2 SUPER ISO 400 although is black and white is processed by C41, which is used to develop colour negatives
This means you can get this film processed at a shop locally that does colour film processing without having to send it off to be developed.