Wireless headset audio input/output
The Bluetooth standard has two profiles for audio with computers, A2DP (Advanced Audio Distribution Profile) and HSP (Headset Profile). Your headphones show up as two devices because of this. HSP is monaural, but includes microphone input. A2DP is stereo, but doesn’t have microphone input. Ideally, on phones, when you’re listening to music and a call comes in, the headphones immediately stop playback and switch to HSP. When you hang up, the ‘phones switch to A2DP and continue music playback. You unfortunately can’t use both profiles at the same time, at least not without modifying the drivers.