The word Goth has been used to describe several things over the years many of which are completely idiotic, whereas others are completely legitimate but surprising nonetheless.
A) The original Goths were an ancient East Germanic Scandinavia tribe. The Goths eventually split into two groups after migrating towards the Baltic Sea: The Visigoths and The Ostrogoths.
Though at one point in time the term Goth was used to describe barbarians (as that is what The Visigoths were famous for) that term is no longer used. Another import fact; neither the Visigoths or the Ostrogoths had their own religion, they were Germanic paganism and Arianism. Implication: Goth is not a religion.
B) Goth was also an old architectural style which began in the 12th century. (An example of this style is St. Denis Abbey or Westminster Abbey)
C) Goth can also used to describe literature. Gothic literature was dark romantic dating back to the 1700's. Two of the possibly most notable authors from the time were Edgar Allen Poe, and Mary Shelley.
D) The most common usage of the word Goth however is the description of a fan of Goth Rock and a member of the subculture. The subculture began primarily with the release of Bela Lugosi's Dead by Bauhaus though some beg to differ and say bands such as Joy Division and The Mission outdate Bauhaus. To belong to the gothic subculture appreciation of the music is essential, while there is more to the subculture than just the music, many people fail to realize that someone fashion choice or attitude does not necessarily make them Goth.
Man those Visigoths sure were barbaric.
Goth! architecture is so beautiful.
I was reading The Fall of the House of Usher the other day, man was that Goth.
Yesterday I ran into my friend, sometimes she's such a pretentious Goth.