From here:
There are a few different variations of the scam, but one version is that sellers create fake customer accounts, buy their own products—usually very cheap or worthless versions of products—and send them to people’s homes in other countries. The online customer accounts might be fake, but the addresses are real, and the sellers can then use those accounts to register real deliveries, post glowing reviews of the products, and improve their rankings on e-commerce sites like Amazon or eBay. Many press reports by local outlets like CBS News, Newsday, and others have described the practice in recent years.