Steampunk as a genre is a nutshell. Steampunk has also cross-pollinated its way into other genres, so there is steampunk romance, steampunk erotica, and steampunk young adult fiction. And it isn’t just written fiction anymore. There are steampunk games (e.g. Bioshock II), steampunk graphic novels (e.g. League of Extraordinary Gentlemen), and even steampunk movies (e.g. Sherlock Holmes and Hell-boy) and TV shows (e.g. Warehouse 13). There is even steampunk music and steampunk performance art.
Steampunk however, has become a lot more bigger and interesting with all the cool contraptions in the subculture, it was only natural that some people would decide to make some of them (or at least things like them). Thus, steampunk gadgets came into the real world. People has “steampunk’d” everything from computers, desks, telephone, watches and guitars to cars, motorcycles, and whole houses. These objects can vary from a grungy look of a forgotten antique to the shiny overwrought newness of a Victorian gentleman’s club. Think brass and copper, glass and polished wood, engraving and etching, and details for the sake of details. So, steampunk is also a design aesthetic. This aesthetic design can carry over into personal style with both clothing and jewellery being made in a “steampunk” style. The clothes are not exactly Victorian, adding in technological bits or hints of a more adventurous life than a typical Victorian citizen likely enjoyed.
Steampunk has a philosophical angle to it as well, which is somewhat a combination between the maker ideals of creativity and self-reliance as well as the Victorian optimistic view of the future. This last bit has led to accusations that steampunk includes a fair amount of empire worship, which is a reasonable concern. Another criticism has been that steampunk focuses on the best of the past and quietly sweeps the bad past away.