What is Napoleon Death Mask?

When I searched the web just now, I was wondering why the hottest keyword is Napoleon Death Mask. Napoleon?! As in Napoleon during the revolution? Honestly, I just heard, errr, read this word just now (or am I missing something?)

So I searched the net for more info about this intriguing mask. From the wikipedia, I have known that there were only four genuine death masks that existed. One of those is of Napoleon Bonaparte.

Now I wonder, what is it for.... Do you know why?