What is a troll? What is a flamer? What is a kook? What is a shill? You'll find a detailed explanation of the various terms reading gandalf's trollfaq (always retrievable through "Archive-name: net-abuse-faq/troll-faq Posting-Frequency: monthly"). Also, in order to understand this lore, you better have already acquired an adequate knowledge of usenet.
As a matter of fact, on any virtual meeting point (usenet newsgroups, http:// messageboards, maillists) you may register "attacks" by individuals interested in disrupting the flow of messages.
There are MANY kinds of such individuals, see for instance the wondrous descriptions of usenet people at [Flame Warriors]
A troll is basically one who posts messages intended to insult and provoke per fas et nefas (see [Trolls and Schopenhauer] below).
For each person who responds, the poster (the troll as a person) will consider that person "caught". The troll (the troll as an action) is considered to have been a complete success if it disrupts beyond repair the normal traffic on a newsgroup or on a messageboard. In extreme cases, trolls are posted by groups of trollers and crossposted to unrelated newsgroups in an attempt to destroy those groups by flooding them with flames and off-topic ranting.
Variants:
1.spamming troll, one who posts -or crossposts on many newsgroups- the same, exact post, multiple times (mostly one liners: "cascade"). Some of these 'listings' with all answers and counter-answers, can grow into huge files.
2. kook: a regular poster who continually posts messages with no apparent grounding in reality. The kook trademark is paranoia and grandiosity. Kooks will often build up elaborate imaginary support structures, fake corporations and the like, and continue to act as if those things are real even after their falsity has been documented in public. While they may appear harmless, and are usually filtered out by the other regular participants in a newsgroup or mailing list, they can still cause problems because the necessity for these measures is not immediately apparent to newcomers; there are several instances, for example, of journalists writing stories with quotes from kooks who caught them unaware. See
http://www.crank.net/usenet.html for more info.
Some people have dedicated their lifes to expose kooks, and they will warn you that 'It is important to note the subtle distinction between a net.kook, a net.cretin, a clueless newbie, troll, or garden-variety @$$hole. The newbie, one hopes, can acquire a clue on the installment plan even if he can't afford to buy one for cash; the cretin is merely stupid and/or irritating; the troll is purposely pulling your leg like it got caught in some heavy machinery, the @$$hole is, well, simply that. But a TRUE net.kook has a special fascination derived from his/her/its utter ineffability. Their behavior is irrational, if not downright weird, but they are seldom merely boring'
A very interesting Kookologists' Manifesto is "The way of the Kook", this makes very good reading and it is much more informative as it may seem at first.
3. A flamer is one who contributes nothing but uninformative "ad hominem" bickering. His inventivity in names-calling and "hurting tooth poking" fears no matches. Even a good troll will never win against a good flamer. Yet flaming is an art that many, many, try, few master, and nearly all think -wrongly- they are good at. So since you (reader) are most probably not a good flamer, heed the (sound) advice: never answer to a troll (not even in order to flame him, see below).
4. A shill is one who posts messages as a spokesperson or "front" for an unseen group or organization, usually at odds to the topics being discussed.