After that section it goes into much more specific detail by listing individual commands. But if that's still too many words, here's a general description: JJ2+ fixes a lot of bugs and adds a lot of things, both clientside and serverside.

The readme is a bit disorganized but it gives a concise description of what the program does, and gives a brief description of how it works. The bit I quoted should probably be in the original post of this thread though. The part of the readme that explains how it works is kind of fragmented (note 1, note 2, note 3, etc) but its pretty simple. It just loads a special .dll file that contains all the fixes. You have two options: either create a special jazz2.exe so the dll loads automatically, or load it manually.

Edit: And sorry if my response was a bit rude, since it basically amounted to "rtfm". I still stand by that reasoning however, as it is somewhat annoying to ask what a program does when the documentation is readily available. Saying "I read the manual but don't understand this or that" is perfectly acceptable of course. The important thing is to at least give it a shot, since otherwise the best you can usually expect is no response at all to your questions... other than something very vague like my original comment, or "read the manual", of course. Explaining things that have already been explained in the documentation isn't fun, especially when it seems like the person asking the question doesn't even care enough to bother checking it first. It kind of wears on you if you deal with this sort of thing a lot.