The Battle Pass is a method Battle Royale players can use to gain access to exclusive in-game rewards.
At the beginning of every Battle Royale Season, every player will gain access to the Battle Pass. This book of rewards provides players content when they reach certain in-game thresholds. Season 4 begins on May 1st and will run until July.
While playing Fortnite Battle Royale, players will earn Battle Stars via leveling their Profile Rank and by completing Daily Challenges. These Battle Stars can then be used to unlock Tiers in the Battle Pass--each new tier includes both Free and Premium rewards.
Every player will receive the Free reward listed under a Battle Pass Tier once they have unlocked it. The Premium rewards on each Battle Pass Tier can only be acquired by purchasing Battle Pass Premium.
NOTE: Battle Pass Premium can only be purchased with V-bucks, and not directly with real currency.
Players can also purchase individual Premium Tiers with V-bucks, even without acquiring the needed Battle Stars. However, tiers can only be purchased in numerical order. For example, if I have not purchased Battle Pass Premium and I want the Premium item on Tier 5, I will need to buy tiers 1, 2, 3, and 4 first.
Battle Pass Premium is retroactive for a Season. For example, if a player has already reached Battle Pass Tier 10 before purchasing Battle Pass Premium, they will immediately gain access to Premium items associated with Battle Pass Tiers 1-10.
On the other hand, bear in mind that Battle Pass Premium only lasts for the current Season. Buying Battle Pass Premium for Season 3 will not grant access to Premium items in Season 4. Similarly, buying Battle Pass Premium for Season 4 will not grant any Premium items from Season 3, regardless of the number of Tiers a player has unlocked in that earlier Season.