Currently im doing my project which is making a VU meter which is react to the audio input from the audio jack socket.My jack socket is like this 3.5mm Stereo Audio Jack. I have no idea what is these pins/legs stand for and how to wire them to arduino. I have searched a lot of this field of knowledge but i still can not get the solution.
How you wire a socket will depend on what EXACTLY is connected to it. In the case of audio it is very unlikely that you can connect it directly to an Arduino.
It will need some circuit between whatever audio you have and the Arduino. E.g. connecting a microphone is very different from connecting the output of a 200W amplifier.
Steve
Thanks for your attention first.I would like to wire the 3.5mm audio jack socket to audio analyzer,which required the left channel,right channel and the ground pin.
The connection is like this: Audio_Analyzer_v2_SKU_DFR0126-DFRobot
O.k. so you're not connecting it to an Arduino but to an MSEQ7 Audio analyser board. That page you linked to already has a wiring diagram and the jack socket page has a datasheet showing the pins. Between them they have all the information you need. Basically the pin at the front (pin1) is ground and the two outside ones at the back are left (pin5) and right (pin2).
Steve