Black Markets Rules!

Black market: illegal transactions of goods or services (because they are prohibited or because the sale circumvents the law: taxes, price controls, rationing, foreign exchange, etc.). It is, by definition, clandestine.

Grey market: sale of authentic products through channels not authorized by the brand (e.g., parallel imports that take advantage of price differences between countries). It is not counterfeiting; legality depends on jurisdiction and the brand's “exhaustion” regime.