The 12 days of gift on iTunes is an official Apple app that lets you stay safe with all the free offers and applications available around the Christmas season.
When you install this app, you get an alert every time that a new gift is available for you. It can be free songs or albums, or apps and games. Whatever the gift, you may be interested to be the owner forever, so make sure you do not miss a day.
12 days of gift is not a new initiative - Apple manages it every year. Install it now, and you'll be ready for more gifts in the coming year.