When you purchase a product on Amazon, Amazon will usually put a verified purchase stamp on the review, signifying that the reviewer has purchased the product, which is intended to make the consumer feel more confident in their purchase because real people have purchased the product that they're reviewing.
Here's a quick article on Verified Reviews vs Unverified Reviews
Note: Using your Kindle Unlimited subscription to rent the book, will normally not produce the verified purchase stamp on the review. You need to purchase the ebook using the "Buy now with 1-Click" or "Want to buy for" link.
