If you own a tire brand, you sell those tires under the brand's domain name. Then you use the generic domain (tires.com) to establish a site that acts as a thought leader in the market (preferably a smaller niche market than tires). You publish reviews, consumer information, industry news-- about tires. This is not done objectively, but is always skewed to favor the brand you own. This may seem deceitful, but it is a common practice in some industries.
Look up the ownership connections between media companies and large brands (for example Las Vegas casinos).
Look up the ownership connections between media companies and large brands (for example Las Vegas casinos).