Cracker wannabes should look elsewhere: this isn't about breakers of computer security, but rather programmers, administrators and similar tech-heads.
The primary editor of this work is Eric S Raymond, who's quite well-known in Open Source circles. The text itself is just what it claims to be: a dictionary of terms, specifically hacker jargon.
ESRs writing is often quite entertaining, and the introduction is well worth reading for the writing and speaking conventions it describes.
A significant number of the terms are now considered fairly archaic, and any given hacker is unlikely to use more than about a quarter of the terms defined, but non-hackers would do well to keep it at hand for when they do need to communicate with a hacker... and everyone else can just read through and be entertained.
You can still find the HTML version of this document on-line; you probably want that instead if you're casually browsing.
This document is also known as either "The jargon file" or "
jargon.txt"