Let's see if I can supplement the above advice. First of all, it's great that you're asking. There is no such thing as a stupid question and I confess to learning most of the probably little that I know from looking over someone's shoulder (either literally or figuratively). And I invite others to correct any misinformation that I pass along here....
First out of the box, get a good shop manual for your bike. They aren't cheap but they're worth their weight in gold. I prefer The Motor Company's shop manual but there are aftermarket versions as well. You can get a copy at your dealer. Just tell them that you want a shop manual for [whatever year and model you have]. Then read it -- it's actually a fairly good read. And you'll learn tons -- not just where things are and how they come apart, but how they work as well.
Second, exhaust pipes consist of three basic parts (overly simplified). The header pipe (which comes out of the "engine" and wraps around the side of the bike), the muffler (which attaches to the rear of the header pipe) and the baffle (which is a perforated tube inside the muffler). The muffler and baffle serves two distinct purposes -- first to reduce the noise of combustion and second to create some backpressure in the header pipe which, in turn, allows the engine to expell exhaust more efficiently. There's a complex theory behind this last purpose (scavenging, etc.) that I won't even try to get into here. But if you're interested, go to the technical pages at J&P Cycles (
www.jpcycles.com) where there is/was a good article on the whole thing. People replace their pipes for one (or both) of two reasons -- to improve the sound (louder and deeper) and to improve performance (factory pipes must meet EPA and other standards so they're pretty restrictive). They do this in one of three basic ways: by removing the whole exhaust assembly and replacing it (from the exhaust manifold on back), by removing the muffler (with the enclosed baffle) and replacing it with slip-ons, or by modifying the performance of the baffle (by removing or shortening it or by increasing the perforations) . I listed these in order of decreasing expense. But the engine is a connected whole -- a change in any one element means that you have to consider its impact on the remainder of the system. Usually any change to the exhaust is accompanied by the addition of a high-flow air intake system (aircleaner assembly) and the adjustment to or rejetting of the carb. This allows the air intake and air-fuel mixture to appropriately match the exhaust (again scavenging and all). If this isn't done, the engine won't run right -- it'll hiccup and burp/fart and it will suffer a potentially substantial drop in horsepower, etc. There are an almost infinite combination of pipes, aircleaner and rejetting options. In some respects choices are driven by economics, in other respects by appearence and sound and finally by the application (i.e., what will one be doing with their bike). You'll see people endlessly debating (what the hell, it's fun) these combinations. Drag pipes, by the way, are pipes lacking a baffle assembly. The exhaust flows out of the engine freely, without restriction. Since some backpressure is required, drag pipes are generally viewed as detrimental to performace in normal applications. But they sound great.... My advice is to get a shop manual, read the J&P article, order a J&P or Custom Chrome catalog (so that you can sense the multitude of options out there), check out the great tech site at
www.nightrider.com/biketech and lurk in the background (I repeat, questions are OK) of the tech forums. You'll pick it up quick. Hope this helped....
To save yourself big bucks, just take the stock mufflers off and find a pipe that will fit down the center and drive the plug out. It will sound a lot better and wont cost a thing. 
