Headphones are important sometimes.  They allow me to listen to an audio source without anyone nearby hearing.
Yes, I agree. They are especially useful when travelling on a bus or airplane.
They convert electrical signal to a corresponding sound.
Have you ever tried the version that vibrates your eardrum to create sound? I tried Google Glass and that is how it worked.
No, I haven't.  That's interesting I didn't know that's how google glass worked.  It's an interesting hands free format.
Yes, I don't know if they still use that method but it was new to me when I tried the first version of Google Glass. I also like the noise canceling headphones.
Is Google Glass still available?  I thought they were discontinued.  They have a camera attached which is very interesting.
The last I heard is they are continuing to develop the technology. I think they are being used mostly for businesses that need the functionality of a face camera.