Infrared headphones, wireless headphones, and bluetooth headphones. Each of these categories of headphones has a techie-sounding name, but at the bottom line of them all is just plain old wirelessness, which is what you basically thirst for in a cordless audio device.
Of the three, both wireless and bluetooth headphones share a similar method of broadcasting and receiving the audio signals. Infrared headphones, on the other hand, operate on quite a different level. All three, technically, are wireless headphones, albeit using distinctive means for achieving the same purpose.
Wireless headphones, in a more restricted sense, are more accurately called radio frequency or RF headphones. Just like their bluetooth counterparts, these headsets use wireless radio frequencies for sending audio signals from a transmitting device (i.e., a base station) to the headsets so that you can hear the sound. However, since many other devices (e.g., cordless telephones, remote-control cars, etc.) also use radio signals for proper operation, RF headphones tend to compete with such devices for pathways. Thus, it is not uncommon for signal interference to be experienced with RF headphones.
RF headphones remain popular these days owing to the wide applicability of radio frequency broadcast technology in many electronic products. Yet, in the light of Bluetooth technology, RF headphones appear simplistic. Bluetooth hasn't completely nudged radio frequency headphones off the grid, though. After all, both types use a similar medium for their signals (i.e., radio frequency). One striking difference between the two is that with bluetooth headsets, no special transmitter base is required. All that you need are at least two bluetooth-capable devices, which you need to bond or pair so that the devices can create a network between or among them. Having created a personal area network (PAN), the devices can share various types of data, including audio signal data.
Infrared headphones, on the other hand, make use of light. It uses not any ordinary kind of light, but the infrared kind. It is a form of electromagnetic radiation whose frequency is below that of the red frequency range in the color spectrum (thus, the name infrared). Infrared headphones work in a similar way to your television's remote control, except that the headset receives light signals from a transmitter and converts them to audio signals on your headset's speakers. The biggest downside of infrared headphones is their need to be always within the line of sight of the transmitter device, or else the connection is broken. On the up side, though, you won't need to worry about signal interference with infrared-powered headphones.
Infrared headphones, wireless headphones, and bluetooth headphones all operate quite differently from one another, but they are quite capable of giving you quality audio in addition to freedom of movement.