One aspect of the game that has always been important is the acquisition of gold, which can be used to buy gear, mounts, and other useful items.
WoW gold is the in-game currency that is used to purchase items and services from vendors, auction houses, and other players. Gold can be earned in-game by completing quests, killing mobs, and selling items to vendors, but it can also be purchased with real money.
Retail gold is gold that is earned in the current version of WoW. Previous expansions, such as "Classic" or "Burning Crusade," have their own economies and gold values.
Buying WoW retail gold can be a convenient way to acquire the gold you need to progress in the game.