The Basics
Headphone plugs are the male connectors of your headphones that plug into your walkman or stereo.
Headphone jacks are the female connectors you plug your headphones into.
Headphone jacks and plugs come in several types and sizes, the most common being the 1/8 inch (3.5mm) stereo mini jack. It is used by almost all portable consumer electronics devices such as CD players, MP3 players, or minidisc players, as well as most low to middle-end home electronics devices and most headphones. Nearly all higher-end home theater or audiophile equipment will use the larger, longer-lasting 1/4 inch (6.3mm) jack, as do larger, more audiophile-oriented headphones. Some Japanese products use an even smaller 2.5mm jack, which is also used for telephone headsets and is almost exclusively monaural.
Luckily, it is easy to connect all these various sorts of jacks to each other due to the wide availability of adaptors at many retailers like Radio Shack.
Headphone Wiring Diagram
/ \
| | <---- Tip
\ /
*===*
| | <---- Ring
|===|
| |
| | <---- Sleeve
| |
*=====*
|XXXXX|
|XXXXX|
|XXXXX|
|XXXXX|
Stereo:
Tip = Left Channel Positive
Ring = Right Channel Positive
Sleeve = Ground
Mono:
Tip = Positive
Ring = Not connected
Sleeve = Ground
NB: There are two kinds of headphone jacks available, open-circuit and closed-circuit. The open-circuit variety is for general use, while the closed-circuit jack has extra connectors usually used to disconnect speakers when headphones are plugged in.