Draft Boosters are for Limited formats, like Booster Draft and Sealed Deck. They're the classic Magic booster pack - 15 cards from the set designed for a balanced Draft experience, plus an ad card or token.

The Lost Caverns of Ixalan Draft Booster Pack contents:
 
15 Magic: The Gathering cards per booster
1 card of rarity Rare or higher in every pack
3-4 Uncommon cards
9-10 Common cards
1 Land card (Full-Art Land in 30% of boosters)
1 Traditional Foil card replaces a Common in 33% of boosters