From PLAYERUNKNOWN'S BATTLEGROUNDS Wiki
Clothing crates are cosmetic items that players can acquire and show off your player in a unique style in-game. The crates in PUBG ranges from a few crates;
- The first one is a free crate that requires a key to open (a key that you have to buy with real currency). This crate allows PUBG Corp to create free DLC packs down the road from new weapons, vehicles, maps and more.
- The second crate is a free crate with no key required. This crate can be purchased by BP (Battle Points), in-game currency that you earn by completing and winning matches.
- The third crate are limited edition crates. These crates like the Twitch Prime crates require no key and are free to get (unless you have a membership to certain services).
- Q: What economy system is used in PUBG?
A: "Our in game currency/points system is known as Battle Points (BP) which is used to open crates. They grant players one random cosmetic item which they can trade on the Steam marketplace, deconstruct for currency or equip on their character." 
- Q: Why do BP crates cost more the more you buy?
A: The reason crates get more expensive the more you buy is to enforce a soft limit on the number of crates you can buy a week. This creates an economy based on our skins. Limiting the number of crates you can obtain a week is important to make sure there is rarity within items so there’s value in the marketplace.
- Q: What day/time do crates reset?
A: Every Thursday at 00:00 UTC.
- Q: Will you be adding Pay To Win elements to the game?
- Q: Do I keep these items after the official launch (after Early Access) of the game on Xbox?
A: Yes, you will keep all items that remain in your inventory even after the official launch of the game.