More about it:
Businesses or organizations often use dark posts to test different messages without cluttering up their main page with many posts.
Dark posts are a type of social media post that allows businesses to test different ideas they have to get feedback on ad campaigns, deliver targeted messages to specific audiences, and publish content that may not be suitable for the main page or intended for a particular group of people. A user can see the promoted dark post even if the user is not following that specific brand.
Adidas published a dark post to promote the sale of their products at discounted prices by targeting their audience, who frequently show interest and buy their products. This helps Adidas gather their audience’s attention by letting them know that they can buy their favorite products at discounted prices, which obviously they would, given the target audience has already shown interest in the product.