Well, this is a very subjective question, so the following is not a definitive list, but an overview.
Questions / discusions on the books / stories / plot / characters etc., but no fan fiction.
Questions on topics that interest Ray, from his biography
"Hobbies include collecting movies on DVD, fine wine, books on the history of Professional Football, and the works of American Illustrators."
If you want to know Rays view on this, or that, asking a question is On-Topic, as it relates to Ray.
Off-Topic is talking about something unrelated to Ray, his works or interests, and where no opinion from Ray is being sought. This often happens when a topic drifts so far away from the original subject, that there is no further relevance, these tend to die naturally after a short while. In general, no thread should start Off-Topic, though there is an exception for Ray, as anything he talks about is in theory On-Topic to him, or better put, of interest to him.
Remember you may also receive answers from members other than Ray, who may have knowledge on the subject in question.
FAQ answers attributed to Raymond E. Feist are copyright by Raymond E. Feist.
It should also be born in mind that the answer given was only applicable on the date written, and to a specific question. You may find further, similar questions, in the FAQ.