Question: I am looking for a good microphone to record a piano. This is whole new field to me. I looked in the Internet and I found a few places stating about what I shouldn't buy, like, dynamic range microphones.

What characteristics should I look for when picking a microphone (or set) to record a piano?

Would recording directly from a digital piano give me a better quality (although with less dynamics possibilities)?

Answer: 
Rather sadly, you'll probably get better results from a good digital piano than from microphones on a real one. Unless it's a really nice piano in a really good-sounding room. You'll have noticed I didn't say "and really good microphones". They matter, but not as much as you might imagine.

If you're after "classical" solo piano sound, record stereo. But remember, an audience normally sees a piano on a concert stage sideways on, from quite a distance. In this case "stereo" will be about placing the instrument in a reverberant space, not about "low notes to the left, high notes to the right". This is a mistake made by the sound sets of many digital pianos.

But you will probably not get the results you want from hiring a concert hall and putting a stereo pair in the best seat! You'll fake the stereo ambience from some combination of close and medium-distance micing, and artificial reverb.

I'll get shot down for this, but I've made some very pleasing acoustic piano recordings with a pair of Shure SM57 dynamic mics. And you may be in a position to try this, with no immediate expense! Do you live in a world of modern performing musicians? Grab a couple of SM58 mics, take the balls off - they become essentially SM57s. (Don't drop them though!).

If you have no gear at all, there's another approach. Buy a Zoom H4n or similar, put it on a stand in front of the piano. You'll be surprised how close the result is to a recording made through much more expensive gear. And even if you progress to more sophticated equipment, a good portable recorder is always useful.
The recording pattern and style of microphone are valid points, as mentioned above, and will help you to work out how you are going to mic up the piano. In this day and age you need to work out what you are recording into. Most microphones have an XLR output and unless you have some sort of [interface](http://www.soundonsound.com/sound-advice/choosing-audio-interface) then this can be very tough. If you are recording into a mixer, this will likely take your xlr input and you can then direct the signal from there. A lot of the time these days people are opting for [USB technology for their mics](http://subreel.com/best-usb-microphones/). Some audiophiles baulk at the idea of using USB, but the tech has come a long way.