How do speakers/headphones work, and what makes certain models better then others?

Question

How do speakers/headphones work, and what makes certain models better then others?

Answer 1

Speakers and headphones are transducers that receive the electrical signals from amplifiers and convert them into sound energy.  The vibrations in the air that our ears can hear.  

Certain models are better than other because they do a better job of converting the electrical signals into sound energy by more accurately reproducing the original sound.  While a cheap speaker or headset can convert the electric signals into sound energy, a lot of them don't do so well.  They color the sound, making some frequencies louder or softer than the original sound.  It takes a fair amount of engineering to get the reproduction of the sound as close to the original as possible.