How Do 3.5mm Jacks (TRS Connectors) Works?

3.5mm jack, TRS or TRRS Connectors
3.5mm jack, TRS or TRRS Connectors

  1. 1. Sleeve: usually ground
  2. 2. Ring: Right-hand channel for stereo signals, negative polarity for balanced mono signals, power supply for power-using mono signal sources
  3. 3. Tip: Left-hand channel for stereo signals, positive polarity for balanced mono signals, signal line for unbalanced mono signals
  4. 4. Insulating rings

It is also termed an audio jack, phone jack, phone plug, and jack plug. Specific models are termed stereo plug, mini-stereo, headphone jack, microphone jack, tiny telephone connector, bantam plug.
3.5 mm jacks earphone that we use to listen the music is known technically as TRS connector.
Three-contact versions are known as TRS connectors, where T stands for "tip", R stands for "ring" and S stands for "sleeve". Similarly, two- and four-contact versions are called TS and TRRS connectors respectively.

Audio TRS Mini Plug, or 3.5 mm jack


3.5mm jacks connection, an insider look!
3.5mm jacks connection, an insider look!
In general, in audio applications, the convention is:
  • Sleeve - ground connection
  • Tip - left channel (for stereo audio signals)
  • Ring - right channel (for stereo audio signals)
  • Ring #2 - other (such as microphone audio or power)
In many computer and modern multimedia device applications, sometimes the sleeve (or the tip) is used to pass power to microphones.

The voltage applied to Tip & Ring drives you earphones, and you listen the music. More the voltage applied to them, more the volume you going to hear at the channel you have preferred(mono or stereo).
Note: Device manufacturers can be inconsistent with how they wire jacks intended for their particular device. Sometimes this is driven by a desire to control the market for accessories to be used with  a particular mobile phone

Some other configuration that you will find are:

How Do 3.5mm Jacks (TRS Connectors) Works?
Courtesy Quora