Section 1: What Is A Troll?
The WWW gives this as a definition:
troll v.,n. To utter a posting on Usenet designed to attract predictable responses or flames. Derives from the phrase "trolling for newbies"; which in turn comes from mainstream "trolling";, a style of fishing in which one trails bait through a likely spot hoping for a bite.
The well-constructed troll is a post that induces lots of newbies and flamers to make themselves look even more clueless than they already do, while subtly conveying to the more savvy and experienced that it is in fact a deliberate troll.
If you don't fall for the joke, you get to be in on it.
The following extract is from a broader expansion of the defining comments given above:
In Usenet usage, a troll is not a grumpy monster that lives beneath a bridge accosting passers-by, but rather a provocative posting to a newsgroup intended to produce a large volume of frivolous responses.
The content of a "troll posting generally falls into several areas. It may consist of an apparently foolish contradiction of common knowledge, a deliberately offensive insult to the readers of a newsgroup, or a broad request for trivial follow-up postings.
There are three reasons why people troll newsgroups:
People post such messages to get attention, to disrupt newsgroups, and simply to make trouble.
Career trollers tend for the latter two whilst the former is the mark of the clueless newbie and should be ignored.