Headphones consist of a high-quality driver element mounted in a small housing with a padded ear-cushion and padded headband to make the assembly fit comfortably. There are two basic types of headphones drivers: dynamic (moving coil) and electrostatic transducer.

In addition to driver element, a number of other features influence the sound of a headphone. The construction of the ear-peace housing has dramatic effect on overall audio quality.

Closed or Open?

"Circumaural" or "supraural" headphones?
The low frequencies reproduction depend of the low frequency resonance of the transducer (dynamic or electrostatic) and the distance between the driver and the ear.
The use of sircumaural earpads prevent the leak of the sound before it reach the ear but some reflections degrade the frequency response.
The supraural (over the ear) design is close to perfect and is used in modern transducers.
The best design is the "head speaker". Here the headphones consist of two small loudspeakers mounted near ( but not tuching) the ears. The only electrostatic representative is ESLAB.

Dynamic or Electrostatic?
Choose the headphone that best matches your audio system and the way you like to listen. Dynamic headphones offer easy portability. They can be used in a great many applications, including with TVs and portable stereos.
For relaxing at home, or for listening for extended time periods, nothing beats the smoothness and clarity of an electrostatic headphones.

Here is an interesting opinion about "Stereo" and Headphones Listening:

"Stereo Doesn't Exist! We all want "concert hall realism" in our living rooms. The music lover returning home from a concert hall performance and playing a recording of a concert hall performance and complaining of "not sounding the same" is right. It is not the same. It is not stereo. That's why. True stereo is totally unattainable, using a pair of Loudspeakers juggled into "proper position", propped up at the one end of the listening room with the listener seated at the other end. The sound from the two speakers mixed with the room reflections, each ear hearing both speakers (crosstalk) is not hearing "stereo". It is only a poor simulation. It should not be called "stereo". Maybe just "bi-channel". High Fidelity speakers in this case is an oxymoron. True concert hall sound means hearing with two ears, two channel signals mixed in the brain, not outside our heads, and scrambled on the way to our heads. Like an egg, it cannot be unscrambled. Super speakers, super amps, three channels, four channels, more channels, rear speakers, side speakers, equalized sound, delayed sound, surround sound, room acoustic treatment, new speakers every two or three years, etc., etc. are all exercises in futility.
Want to hear the closest to realistic sound reproduction? Tryheadphones. The complaint about headphones that "sound is inside the head", as when listening to mono through them , can be the result of poor separation within the system, such as crosstalk in the cartridge. One advantage of CD is perfect separation. Partly to blame is the microphone positioning. This is primarily done for playback using speakers, or a mix of microphones (scrambled sound again). Too great a distance between the mikes is not good. Your ears are not ten feet apart. Nevertheless, with any stereo source, the closest to concert hall realism is obtained only by the use of the headphones. "Inside The head" sound can be alleviated by playing the speakers at reduced volume while using the headphones. The speakers will be heard as ambient sound as a result of the slight delay of sound from them, which helps in moving the music out front. The so-called binaural recordings made with the kunstkopf (artificial head) are a further attempt toward realizing naturally reproduced sound, and make for exciting listening. Get a pair of good headphones, put on a record of one of your favorites, dim the lights, sit back, and enjoy the absolute sound...."
-Whitney Vreeland
Portland, Oregon