Help me interpret this audio jack schematic
The schematic is a bit confusing, or this is a multi-purpose connector. It is being called a stereo jack, yet pin call-outs are (1)=GND, (3)= TIP, (2)=RING, as if it was a telephone switch-board jack from many decades ago.
In the days of mechanical switchboards this connect/disconnect feature allowed a used jack to light a small lamp. Each jack had its own telephone line to a house. In my Army days in the 1970's I had to wire up a switchboard upon arriving at a location. Each platoon had its own phone and ringer handle.
As a stereo jack pin 1 = GND or common return, 2 = Right channel and 3 = Left channel. If present, pins 4, 5, and 6  are for routing the sound to speakers, such that plugging in the headphones disconnects the speakers.
In todays stereo's speakers should be disconnected if headphones are plugged in. Normally headphones have series resistors of a few hundred ohms to prevent blowing out the headphones, which have nowhere near the power rating of speakers. To make the headphones sound &quot;loud&quot; the volume setting might be too high for speakers, or too loud for the neighbors, so it is just as well if speakers are cut off when the headphones are being used.