Steampunk is essentially a literary genre based on Victorian science fiction, but written by modern authors. Think Jules Verne or H.G. Wells, if they had knowledge of all the technology to come. It is the future as the Victorians would have dreamt it. It is a re-writing of history, a romantic re-imagining of the past with anachronistic elements from the future. It is an exciting, elegant, adventurous, inventive time of scientists, explorers, aviatrixes and airships.
Steampunk has also become an Aesthetic or an appreciation of the beauty of anything old, rusty, mechanical or interesting. This is often a very broad, undefined usage of the word.
A subculture has grown out of Steampunk as well that embraces do-it-yourself, hands on crafting or making as we call it, recycling, giving new life to old and obsolete things. The subculture is ever evolving and often has little in common with it’s parent literary genre just as the Goth subculture has little to do with it’s gothic origin.
Steampunk tends to be a very active and creative pastime with a lot of dressing up, tinkering and having tea.