You could say it's a big art festival that features large scale art installations, many of which are burned at the end. Sort of a meditation on the impermanence of things while legally getting in touch with your inner pyro. But many participants create their own art, usually on a much smaller scale, but often just as impressive in their own way. The creative and engineering skills on display out there are mind-blowing. Nighttime tends to be a big party, with lots of dance clubs and colorfully lit contraptions roaming around. There is art on display at night too, often using light in amazingly creative ways. You can find a couple pictorials from this year's event
here and
here.