Goth is a popular subculture based on both visually and emotionally dark themes, such as Halloween and the Biblical apocalypse. Goth styles range from the elegant, sometimes based on medieval through late 19th-century aristocratic fashions, to the bizarre and sometimes painful-looking modern twists. Some distinctive characteristics are: the excessive use of black or desaturated colors; massive silver jewelry; crumbling stone structures such as ancient buildings or grave markers; overgrowth; depressing (sometimes Heavy Metal) music; and symbolic representations of danger belying beauty such as thorny roses, fire, winter, night, or seductive monsters.
The term "nonconformist" is sometimes used interchangeably with "Goth" and other superficially similar (dark palleted) subcultures such as "Emo".
Many Steampunk enthusiasts were once (and maybe still are) fans of Goth. There is even a rumor that Steampunk came into being “when Goths discovered brown”. But, if that rumor were true, then there's no accounting for how Science-Fiction got involved, for unlike Steampunk, Goth is NOT inspired by technology. Because of this crowd-sharing between Goth and Steampunk, there is often very blatant artistic overlap. I.e. when everyone at a Steampunk convention seems to be wearing mostly black, even though they've accessorized with welding goggles and elephant guns. Debates have broken out over examples like this, usually concluding that it's "Steamgoth".
Personally, I prefer to keep my genres separate and well-defined. I like both, but “Steamgoth” doesn't do anything for me. It's like mixing sparkling cider with chocolate milk. But, hay, whatever floats your ghost-skyboat.