It if pretty much a digital set top box inbuilt so you can watch digital television. Most LCD TV you have to buy the box separately to get the most of watching normal TV in HDTV on it.
What the DVR is the LG model with a built in HDD. All it does is record TV, so you don't need a DVD recorder or a VCR. With these feature when you are watching TV live and you miss something, you can actually rewind it and see what you missed.