4chan is an English-language image board that was created in 2003 by Christopher "moot" Poole as an American version of the Japanese Futaba Channel (2chan). He translated the source code of the Japanese image board to English, then started up what has been the most famous (and infamous) English language image board of all time.
4chan was originally created for the discussion of Anime, but has grown into a collection of image boards dedicated to all sorts of topics. Posting is anonymous, though nicknames can be used.
However, it isn't just images 4chan is known for. 4chan has been the birthplace of lots of internet trolling, contributed a lot to the culture and formation of Encyclopedia Dramatica (both its former and current incarnations), started a ton of internet memes, and has been the center of a ridiculous amount of publicity, both good and bad. By 2015 however, a changing of a guard came when "moot," following a period of drama and controversy finally resigned from running 4chan and now working for Google. Time will tell how this will affect the site in the long run.
- Defector From Decadence: 8chan, after a fashion. Given that a good portion of its users were originally from 4chan, who migrated for one reason or another.
- GIFT: There is a very good reason this site is called the "asshole of the internet".
- Memetic Mutation: Tons of memes have been born due to 4chan.
- Rules of the Internet: Created thanks to 4chan.
- Rule 34: The amount of this you can find on 4chan is mindboggling.
- Troll: Tons of these can be found on 4chan too.
- We ARE Struggling Together: The various boards don't always get along, which can be an understatement.