What is a Authenticity Certificate Card?

This is a card that will come with various items to prove it's authenticity. For example, all you women who have real Prada or Gucci handbags recieved a card stating the maker of the bag, what maks the bag authentic, sometimes it lists special features of the bag and it typically comes with a code such as a number. This is because the real bags are under warranty so that number is useful at times, it keeps track of how many of a certain bag is sold and it is proof you have an authentic bag or if youre questionable about the bag and it did come with an authenticity certificate card you can find out if it is indeed a real bag and not a knock off by simply calling the company and giving the code/number.