#1
hi i'm want to get in jazz band someday in school, what should i learn about jazz, chords, theory others things, what are some good jazz guitars and jazz fusion guitars?
#2
You'll have to learn some fairly complex chords. Some of the ones you should know are 7, 9, maj 7, maj 9, m7, m9, 11, 13, 7b9, 7#9, m7b5, and diminished (a minor chord with a flatted 5th) chords. Seeing as your just in the school jazz band, you probably won't be doing much other then comping, so if you're not planning to pursue jazz outside of jazz band, it's more then likely that you won't have to know too much outside of all the chord extensions I mentioned above.

However, if you are interested in becoming a jazz player (or at least using jazz as a large part of your style) then there is much more you need to know then could be explained in one post. Jazz is a language that takes years of training to be able to master (and even then, there's always more to learn), and I myself am very far from mastering the language (though I don't intend on becoming purely a jazz player). In this scenario, you should start by learning the major and minor scales and all of the modes, work on your notation reading skills, and just listen to a bunch of jazz.
#3
I keep asking myself the same question.

I'd like to see how this thread turns out. I think the most important thing to work out is what keys jazz is made up of and some of the most important chords as ohhey9040 mentioned and how to form them.
#4
You need to familiarise yourself with alot of the more 'awkward' keys; alot of the flat leys for example. Become comfortable with the harmony and also generally learn all chord extensions. The more you learn and become comfortable with, the more you can express yourself as a player. The same goes for scales, modes and arpeggio's. You need a good amount of fretboard knowledge. Its all well and good knowing your theory but the passion needs to be there.

But aside from all the nitty gritty, just listen to alot of the pioneers and modern artists, learn tunes, get involved with it and immerse yourself in it. It will take alot of dedication and true passion of you really want to pursue it.