Affordable Good Listening
While many moderately-priced earphones are specifically designed for listening while you are in motion, I didn't limit my roundup to them. You'll also find lightweight but significantly bulkier earphones and even some that are closer to being good size pro models. Here I use the term "earphone" to encompass all forms of earphones and headphones.
The type of earphone and the method used to couple it to your auditory system will determine both the appearance of the device and what you can and can't do while wearing it, as well as many of the qualities you can expect the earphone to have.
In my opinion, the open earphone gives you the best listening experience, because it covers, but does not surround the ear and allows sound travel naturally through the various convolutions of your ear, while still letting ambient sound in. This type is generally more comfortable to wear for long periods and also does a better job of rendering the "soundstage." On the other hand, open audio-phones are not the best for listening in noisy surroundings, such as in the street or while you are on public transportation. They are also less desirable for certain uses such as monitoring (for DJs, musicians, and sound technicians), since you're disturbed by the exterior noises that reach your ears with practically no attenuation.
Closed earphones, as their name implies, fully enclose your ear inside a closed volume of air. They provide a certain degree of acoustical isolation from external noises - but that isolation is always relatively low and works best in the upper audio range. Closed systems work best when they include an electronic noise-reduction system, which attenuates noise in the low and low midrange frequencies. I haven't included closed earphones in this roundup, since their price is almost always beyond the price threshold set here. I should point out, though, that closed earphones also have the advantage of not disturbing others as you listen to your music.