Cycling jerseys come in myriad forms. I define cycling jersey as a top that has pockets in the back, that distinguishes the true cyclist (aka Serious Cyclist) from the great unwashed who are seen riding around in t-shirts, tank tops, and what not. You've probably graduated to a cycling jersey shortly after you graduated to cycling shorts and discovered that they had no pockets at all and you needed somewhere to put your keys.
In the old days, jerseys were made of wool. The flashier ones sported two colors, maybe a solid color with a racing stripe down the middle. Nowadays, wool is out of fashion, so anyone seen in one is either a randonneur or an ancient like myself. If you see the name "Eddy Merckx" on it, it's probably the latter.
Then there was the era of the polypropylene jersey. It was in this era that I acquired my Nashbar jerseys, two colors with a diagonal division. Not very stylish, but I never found that to be an issue (as Mrs. D. will attest). The problem with early polypro jerseys is that they were an odor magnet.
Then there is cotton, a substance universally reviled by the cognoscenti since when you combine cotton, cold weather and sweat you are dicing with hypothermia. But cotton is very comfortable, and some people (notably Mrs. D.) don't like being encased in hydrocarbon products. There's a real advantage to wearing cotton jerseys commuting, namely, they don't smell as bad as synthetics. In my old building I had an office, which people regarded as a superfund site, but at least I could close the door and not offend the passersby. My new setup is basically a cube farm, and the jersey aura will radiate far and wide. I've also got a homemade one that I fashioned by sewing a few pockets onto the rear of a CRW t-shirt, in the manner of my mentor, Eric Ferioli.
When the Tour de France became somewhat main stream thanks to the likes of Greg LeMond and Lance Armstrong, people started wearing jerseys of their favorite racing team, or facsimiles thereof. Around that time I joined NEBC and acquired a bunch of real racing jerseys cheap. I never actually raced, but I looked cool. Then there are the designer jerseys, a la Primal Wear, like the frog ones. One of my favorite jerseys has a beer theme, with logos of many beers I have yet to taste. So many beers, so little time.
Real jerseys have pockets that are remarkably expandable and I have stuffed incredible amounts of stuff in them: wallet, food, jacket, garage door opener, camera, cell phone, various road scores. In our tandem days, Susan found my jersey pockets a handy glove compartment, so after a ride I would find all sorts of detritus in there, used Kleenex, etc.
I've seen ads recently for a "comfort" cycling jersey. This looks like a baggier version of a real jersey, which is skin tight for aerodynamics. Seems a slippery slope from that back to the t-shirt, only with back pockets. Its claim to fame is that you look more like a normal person, not a bike weirdo. If that's your aim, you might as well just wear a regular shirt, you still look like a marsupial with this one.