Sometimes called "offer pages", "match pages", "product landing pages", these pages are created to drive more qualified traffic to your store. If the CSE knows that your product is identical to another retailer's product, it will usually bunch them together on one of these types of pages. These are great pages because they drive more qualified traffic to your store, compared to a listing on the main search page, where you may get a lot of clicks, but likely fewer sales.
So how does the CSE know which products are the same? A CSE will compare your data with other merchants. Most importantly, they compare unique product identifiers such as MPN, UPC, ISBN. Alternatively they may use keywords in your product name and description. If they see a strong match, they will combine your listing with other merchants selling the same item.