Mic Headphone Jack to Combo 3.5 mm Plug Stereo Adapter Cable 2-in-1
It is a Y adapter audio cable.
It converts 2 plugs old headset to work on 1/8" (3.5 mm) combination headphone/speaker jack computers or cellphones.
Connector:
3.5 mm 4-conductor TRRS phone plug
3-conductor jack (headphone/microphone jack)