2ch (2ちゃんねる pronouced "nee-channel"), opened by Nishimura Hiroyuki in 1999, is one of the largest BBS in the World (largest in Japan). With over 10 million visitors every day (as of 2001), it is gaining significant influence to the society, approaching to that of traditional mass media such as TV, radio and magazines.
What is unique about this BBS is its scale and its management style. It has more than 100 "board groups" ("ita") each with its own categorical topic (ex. "Social News", "Computer", "Cooking"). Each "ita" usually has hundreds of "threads", which is an actual discussion page created by anonymous visitor for each detailed topic (ex. "Coming election in Tokyo, 4th vote", "P4 vs. Athlon, overheating 51 times", "Best wheat for making Pizza, 3rd slice"). Every posting in a thread has "age" (up) and "sage" (down) attribute, and once posted with "age" attribute (default), that thread goes to the top of recent active thread in its board group. Each thread is limited to 1000 postings at maximum, and must be recreated (by some anonymous user, self-elected during discussion) to continue discussion. This prevents the rottening of old threads and keep active topics refreshed. Most "old" threads will be stored in a thread archive after deprecation for future reference. Nearly everything is done anonymously (and voluntary).
With huge popularity of this BBS, this "thread floating with pushout style" BBS is now known as "2ch-style" BBS.
Several important and/or well-known social issues (incidents, social movements) are known to have relation with this BBS, and due to early shocking events (murders, etc. See Neomugicha incident), this BBS is somewhat acknowledged as "underground-ish" BBS despite its wide acceptance, especially in younger generation. OTOH, these incidents helped 2ch to have huge publicity through mass-media coverings.
Frequent visitor of 2ch BBS is usually called (and call themselves) 2ちゃんねらー (2ch'er, pronouce "nee-chan-ne-rah"). Even though topics vary a lot between each thread/ita, 2ch as a whole keeps its unity though its unique cultural backplane. "2ch slang", "2ch AA (ASCII Art)", "2ch Flash" are example of such culture. Many virtual characters, such as Mona, Onigiri have evolved out from these creations, and now acknowledged as a mascot representing whole community.
Although its scale and broadness of topics is uncomparable, some may find 2ch to have cultural similarity with Slashdot. They both have grown out from small, niche community (subculture, underground, technology, etc), and has become so large that they are not "niche" anymore. One notable difference is probably the policy against trolling/off-topic posting: while Slashdot tries to "moderates out", 2ch "embraces" it. Due to this policy, troll/off-topic posting in 2ch have made its own advancement and many are now part of 2ch culture.
Some may also draw resemblances to Something Awful.
To this date, official owner of 2ch is Nishimura Hiroyuki, known as "hiroyuki" (ひろゆき). But most daily management is done by external voluntary group self-elected and picked from 2ch visitors. 2ch itself is non-commercial and run by banner advertisement fee and support from a hosting service company that provides specially priced inexpensive UNIX hosting.
Due to its chaotic nature and hugeness, it is difficult to describe/define this emerging community. Several movement to self-describe this community have been running, and so the reader is recommended to visit these materials.
See also: Mona Font
2CH is also a Sydney easy-listening radio station, 1170 kHz AM.