This adapter converts a stereo 3.5mm cable to mono. This adapter wires the tip and ring of the stereo side to the tip of the mono side. This ensures that you will get all the audio information from both stereo channels.
This is a TS or mono plug (note the single stripe on the connector) This provides single channel analog audio.
TRS (Stereo) Plug (Male)
This is a TRS or stereo plug (note the two stripes on the connector) This provides a stereo or 2 channel analog audio. Commonly found on headphones
TRRS Plug (Male) 4 Conductor
This is a TRRS 4 conductor plug (note the 3 stripes on the connector) This can provide 2 channel audio plus a microhone. Also capable of 2 channel audio and a video feed. This is commonly found on iPhone headsets and portable DVD players.