Unlike most Google tools, this one is not free. The Google Commerce Search is aimed at large and small retail enterprises with commercial websites that enable fast and efficient search of your products and services.
If you are managing a vast portfolio of diverse products and brands on your e-commerce site, the Google Commerce Search will help your customers find exactly what they need with the least time navigating through your site. You get better conversion rates that turn visitors into paying customers.
The tool is essentially a search engine for your retail site, allowing spelling corrections on searches and filtering algorithms on price, brand or any product attribute and generally optimized for the purpose of getting more sales.