Could be a 'line-out/line-in' cable? If so, they're used to connect, say, a phone to an amp or to anything that may have better speakers and that has a line-in socket. May also be used in a car if the car stereo is old and has a line-in rather than bluetooth.
We have an old (very old) car with a stereo/cd player, so I bought an FM transmitter that could play music from a phone, card or usb (and then transmit the music on a 'free' FM channel that the radio is tuned to) and those cables are used for that.
Technically, it's a stereo (or 3-pole) 3.5mm jack male to male audio cable. As other have said, virtually useless these days (until you suddenly need one, of course. )
A trowel in the hand is worth a thousand lost under a bush.
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Also, label the plugs so that when they are plugged into an extension lead with multiple sockets you can easily see which is which.