Reviews can appear on a variety of places on the web, including your own website and third party sites like Facebook, Tripadvisor, Amazon, Twitter, Yelp, Check-a-trade and much much more. But the glue that binds all of these sources of reviews together is Google. Once reviews are published online, Google can aggregate them by reading their content from those sites, and it presents reviews within the sort of organic or paid reviews on Google search results.
These Google Business Reviews are then presented to users who enter relevant search queries. For example, if you were to search for a company into Google, you’ll likely be presented with a list of results, including, many others, the company’s official website, it’s Facebook page, perhaps listings on Amazon, and (if it’s within the travel/tourism category) an inventory on Tripadvisor