These IR repeater and extenders let you extend the range of your IR remote control.
When you hide AV equipment in a closet, cabinet or furniture, or place the equipment in another room, the infrared beam from the remote control can no longer get to your electronics. IR remote repeaters solve the problem by placing a "receiver eye" in plain view where you will point your remote control. This eye is wired to a little hub that connects to one or more IR emitters that are placed on or near your hidden electronics, allowing them to be controlled when out of view.
IR extenders and repeaters can be used at home, in bars, meeting rooms or offices to let you hide your AV gear out of view without losing control.