The Best tab will contain 4 packages available. These items provide you with a daily item for free, some packages when exploring places, food, and equipment.

Secret Box: This provides you with a free item on random. You'll need to watch an ad first and complete it, and the award can be claimed every hour.
Exploration Pack: Opening this pack gives you a chance to get a first aid kit, or Weapons of differing rarities.
Survivor Pack: This pack provides you with food items, as well as a Weapon.
Special Forces Pack: Opening this pack gives you a chance to get some Meds, Armor, and Clothes. Useful for their stats.