Such kind of a question, in general case, is just not quite valid. I don't know if you interpreted the source you've read correctly, but maybe some of them are also invalid. In this case, they are not the same and not different: one is the kind of another. Please read about them:
http://en.wikipedia.org/wiki/Piconet[
^],
http://en.wikipedia.org/wiki/Personal_area_network[
^].
It clarifies this purely terminological issue, doesn't it?
—SA