It's a service where you sync our credit card information with your G-account.
When you rate and review another post in Google+, you spread your name not only through the search engine, but also get attached to Google Maps, if that person or business has allowed such a tag - and they should have. If webmasters of other sites that Google thinks are in some way relevant to widgets see fit to send traffic to your widget site, then that confirms to
Google that human beings will perceive relevance.