Soundbar and subwoofer makes your TV sound better
What it does is connect to your TV set, which then routes all sound through to the soundbar, then optionally also wirelessly routes the audio on to a subwoofer. If I truly understood what a subwoofer was, I might be better able to measure the difference all this made. As someone who just likes TV, I can only tell you that the difference is loud. As someone who can read the spec sheet, I can tell you that it's 120 Watts and Dolby Digital 2.1 Channel Sound.
Have a look at Kitsound's promo video for this. It doesn't show you much, doesn't tell you much, but you'll get a sense of the scale of this next to a TV set in a far tidier living room than we've got.