I've listened to Goa/Psy Trance for half my life now, and many times I have found these terms to be interchangeable, like searching in youtube suggests. And while there's even separate wikipedia pages for them, I can find
Goa/psytrance in the Goa page, or
Goa being used to refer to
Psychedelic Trance in the page of the latter.
Even if I tried to search for music of both genres to compare by listening, I could never be sure that they were properly labelled.
So, is there a difference between the two genres? If yes, how can one tell if it's one or the other? If no, why the different nomenclature and history reports?