4chan.org is one of the most trafficked online imageboards in the world. It was created October 1st of 2003 with the original intent of discussing anime and manga. The creator of the site, Christopher Poole, (who goes by "moot") was inspired by the site "2chan". 2chan which is an imageboard similar to 4chan, was also used to discuss anime but it was in Japanese, so moot made an english imageboard to have the same general subjects.
The following introduction is posted to the front page of the site:
"4chan is a simple image-based bulletin board where anyone can post comments and share images. There are boards dedicated to a variety of topics, from Japanese animation and culture to videogames, music, and photography. Users do not need to register an account before participating in the community. Feel free to click on a board that interests you and jump right in!"
This description is accurate, yet feels somewhat disingenuous to someone familiar with the site. While there are many boards you can peruse and post to, the site's real claim to fame is one particular message board, "Random". Random also known as "/b/" (WARNING: POTENTIALLY EXTREMELY NSFW CONTENT ) is 4chan's random posting board, where people may post anything that crosses their mind. This can range from interesting, to inane, to viscerally disgusting, but all topics are free game.
When 4chan.org was brand new it had two boards: /a/ (anime general) and /b/ (anime random). Over the years it became necessary to add more boards. There are now fifty-three boards, seventeen of which are directly influenced by Japanese culture, though most pages of 4chan will contain an image with Japanese origins.
4chan.org can represent both the best and the worst of uncensored media. It offers a view of what can be produced by pure unfiltered user content in cyberspace. While there are moderators who are constantly IP banning users for their transgressions, it usually takes a lot to get banned, as most things are allowed on 4chan. Although you should carefully note that while each board has "Global" rules and then its own set of rules to deal with specificity under the section for /b/ it simply says "ZOMG NONE!!!1*" the asterisk following up with "Note: 'ZOMG NONE!!!1' applies to moderators as well."
A lot of the attention that 4chan.org has received over the last couple of years is from an internet meme that was started there in 2003. That meme is Anonymous which was an idea used to explain the sense of an "anarchic, digitized global brain". This collective quickly became well known on the internet for trolling other sites and causing mayhem . However, only very recently has Anonymous been brought to the forefront and into mainstream media. This is one part of the amazing hacking talent that has gravitated toward these boards making it possible to take down big targets in order to get their agendas across.