Please visit:
http://www.proz.com/translation-articles/articles/95/Definitions
Of course, it is necessary to define what constitutes a PRO or a non-PRO question. While there may be no way to draw a clear-cut line, the following definitions have been adopted for the two types of question:
PRO questions are those that are asked by OR that are suitable for professional translators.
Non-PRO questions are those that are asked by people who are not professional translators, and that can be answered by any bilingual person without the aid of a dictionary.
When applying the above definitions, detach yourself from your own background/specialisation and think of a - hypothetical - randomly selected bilingual person. Is it likely that this person would be able to produce a good translation of the term or phrase in question (and in the particular context shown) from the top of his/her head? If not, it is a PRO question.