It's a ''happening'' that grew out of the North American counter-culture movement that developed from the mid 1960s and a dwindling number of the attendees took part in some of the original events. It takes place in Black Rock City every year and its principal ''event'' is the UltraMarathon of 31 miles. The evangelical right despise it, without ever having been to it of course, and proclaim it to be part of the burgeoning wave of Paganism (capital P) enveloping the US since the election was ''stolen'' from them.
I've seen it described as yet another attempt to create Utopia on earth. I believe paying for anything at all is banned, but trading is allowed, and there is a ban on anyone performing toilet functions other than in the surprisingly few structures provided, which is riguorously enforced. Not everyone's cup of tea, including mine, but I see no harm in a group of such like-minded people meeting and sharing without being hassled and harassed.
P.S. This has no connection to the Pagans motorcycle gang, originally from Philadelphia, which vies with the Hell's Angels to be the most lawless in the USA/Canada (i.e. astoundingly criminal.)