Most new TV does not have an RCA audio output. Some now have a mini jack headphone socket or you can use the optical output to connect to your AV receiver digital input. However if either the length is too far or you are wanting sound back out of TV into your 2ch stereo (that does not have digital input) you will need this little box.
This box will convert the optical sound out of your TV into analog to plug into your stereo.
The picture shows 3 boxes all the same, you need just one at the TV end. It can be powered by the TV USB port or a separate 5v power supply $30.00