Back in 2015, Blizzard introduced an item into World of Warcraft called the WoW Token. Available for purchase via cash or in-game gold, players who have this token are able to redeem it for extra game time or auction it off for in-game currency. Starting from today, you can also redeem said WoW Tokens for Battle.net credits as well.
With this new system in place, players who’ve decided to do so can now trade in their WoW Tokens for USD15 worth of Battle.Net credits instead. The player’s Battle.net account would be updated to reflect the balance. Once the money is in their account, they can decide to spend it on in-game purchases on other Blizzard games such as Overwatch Loot Boxes or Hearthstone Card Packs. If the player has enough Tokens to burn, they can even save up the balance to purchase a new game from the Battle.net store itself.
Although this system may seem like an easy way to get Blizzard games or in-game items, do note that WoW Tokens usually cost quite a bit of gold in game. Depending on the server you’re on, a single WoW Token may cost up to 100,000 in-game gold. Needless to say, the only people that will be able to purchase WoW Tokens in bulk to exchange for Battle.net credits are those that play with the Auction House.
Source: World of Warcraft