Basically it's a device that has one HDMI output (to the tv) and a various number of HDMI inputs (DVD player, DVR, game system, and so forth) with a remote or button to cycle through the various inputs.
War, what he means is he wants only one HDMI cable running from the tv into the fireplace instead of one HDMI cable going to the tv from the cable box and one HDMI cable running to the tv from the DVD player. What he needs to do is use an HDMI switcher.
Thanks WarEagle, my problem is that I have mounted my TV on my brick fireplace and set the DVR inside the fireplace that is never used and sealed up. So running another cable out from thru the glass fireplace screen to the the TV will be difficult and unsitely.