There are largely 3 different technologies that make this possible.
Infra Red ( Monster Beats by dre IR ) headphones use the same technology as your Television radio control.
2 , the range is restricted to about thirty feet.
The most recent technology for the wireless life is, of course, Bluetooth.
This enables PCs to hook up with printers wirelessly, for instance.
Bluetooth enables one to listen to music and answer telephone calls when driving.
This is a giant and when it comes to safety.
( Not a difficulty if your music player is in your pocket, bag or backpack. )
Some are over-ear headphones for top quality sound when you are in your house.