What does "Jetted" mean? What does it do? Is it easy for a noob to do on an 02 Warrior?

 

They're located in your carb and provide fuel for the air/fuel mixture. I guess a bit like injectors. I wouldn't jet the quad until you had a few aftermarket mods. Such as exhaust, air filter and box set up. I would suggest trying to install the parts all at once, and only need to jet once. Unless you go beyond those upgrades...

Edit: I guess I should have explained it like this: The more free flowing mods you do (like the ones I listed), the more fuel you're going to need to compensate for the extra fuel. Need to keep the air/fuel ratio in spec. Larger jets will allow for more fuel. That's... basically the concept.

 

There are a bunch of precision sized, holes in the carb, which meter the air and gas. If you change the exhaust or intake, youll change the amount of air and gas which flow in the carb. Rejetting gets the mixtures correct again.
Heres a couple of articles, which explain it pretty good.
jetting
carb 101
how it works