Of course it's important, silly.
It's hugely competitive. The BBC broadcasts the games.
The great thing about the competition is that the bigger teams (England and France) do get beaten and smaller teams can run away with the competition. For example,
Scotland beat England last year which was not expected because English rugby is traditionally and has in latter years been very strong while Scottish rugby has been weak for a number of years now; Wales won a Grand Slam a couple of years ago (beat everyone else) with a superb exhibition of style and energy not seen from them for years, if not decades. Italy are relatively recent to the competition but, despite being regarded as the whipping-boys, have defeated both Scotland and Wales in previous years so are improving all the time.
It's an aggressive sport - if it's fast and open it can be exciting and very entertaining; mauling style of play can be quite dull, unless it's your team mauling the other guys. Even if your team doesn't win you might still, as a fan, be rewarded with a view of one or more of the opposing team well-rended or even, stretchered off; but I digress.
edit: wiki page:
http://en.wikipedia.org/wiki/Six_Nations_Championship