What is Fukubukuro?
Fuku means “Lucky” or “Fortune” in Japanese.
Bukuro(Fukuro) means a bag. So… fukubukuro福袋（ふくぶくろ） is a lucky bag.
These bags are sold in new year and very popular in Japan. People make long lines to get these bags from early in the morning. They think it is a good bargain to purchase Fukubukuro because the merchandise stuff many of their items in one bag and sell cheaper price than purchasing these individually.
It is notified, for example if this Fukubukuro is fashion items, the size and how many and what kind of items are inside, but what are exactly inside is left unknown. You will know when you open the bag after buying it. So, this Fukubukuro is also a “mystery bag”.