Ahhhh, espresso. Nectar of the Gods. My drink of choice. Where to begin? First of all, espresso is made by forcing very hot water under high pressure (about 9 - 15 bars) through finely ground, compacted coffee. Tamping down the coffee promotes the water's even penetration of the grounds. This process produces a syrupy beverage by extracting both solid and dissolved components. It also produces the definitive crema (a thin layer of foam at the top of a cup of properly extracted espresso) by emulsifying the oils in the ground coffee, which does not occur in other brewing methods. It's syrupy, bittersweet and oh so damn good! :starrylov
The grinder is more important than the machine in making good espresso. It takes time, practice & technique to consistently pull cafe quality shots at home. But once you're "dialed in" (finding the perfect grind setting, tamping pressure and pull time on the machine), the reward is heavenly. Espresso (and espresso based drinks like lattes, cappuccinos, macchiatos, mochas and americanos) are all I drink at home. I like it so much, that it's a let down to drink "regular" brewed coffee at work now (mind you, I'm still using super fresh, home roasted coffee and the best equipment out there, but it just doesn't taste the same as true Italian espresso).
Espresso is both a coffee beverage and a brewing method. It is NOT a specific bean, bean blend, or roast level. Any bean or roasting level can be used to produce authentic espresso. For example, in southern Italy, a darker roast is generally preferred. Farther north, the trend moves toward slightly lighter roasts. I experiment with roast level and rest time on my home roasted beans to find the perfect roast for pulling espresso shots. A bean that is really good prepared as drip (or press or whatever), could be thin, underdeveloped and sour when pulled as an espresso shot - it just takes knowledge of the bean (and seedstock, but that's a whole other conversation) and just good old fashioned experimentation to find out what coffees are good for espresso usage and which ones aren't.
If you want to get into espresso, my advice would be to first & foremost, consistently buy (or roast your own) fresh, high quality coffee and then get an entry level Gaggia machine and pair it with an entry level, espresso-only dedicated grinder. Here are a few I'd recommend to start your search out with:
Machines:
http://www.wholelattelove.com/Gaggia/gaggia_evo_black.cfm
http://www.amazon.com/Gaggia-102532-Espresso-Pure-Semi-Automatic-Espresso/dp/B0015QX3BG
Grinders:
http://www.wholelattelove.com/Gaggia/mdf.cfm
http://www.zaccardis.com/nemox-lux-plus.html
I tried to summarize without getting too in depth, so I left many things out so I didn't write pages and pages. Hopefully this helps you out and don't hesitate to ask questions if you need to along the way. :waving: