"Black oud" typically refers to a type of oud oil that has a darker, richer, and more intense aroma than other types of oud. Oud oil is derived from the agarwood tree and is highly prized for its woody, musky, and slightly sweet scent. "White" in perfumery usually refers to a scent that is light, fresh, and airy. It could refer to a specific note, such as white florals (jasmine, lily, etc.) or white musk, which are often used in perfumery to provide a clean and pure scent. Combining "black oud" and "white" could suggest a fragrance that blends the intense and earthy aroma of oud with the light and fresh scent of white florals or musk.