To include rich searching functionality into your website, Googles Custom Search Engine (CSE) is the best way to include in your website. Custom search allows you to create search engine for website, blog or a collection of websites. By using Google CSE you can add your own promotions, configure web page and images, customize the look and feel of search result and also it will allow you to eliminate any unwanted website or information.
Magentos default searching functionality is limited to one website. But if you want to provide custom search in your website than Google Custom Search Engine is a good option. Google Custom Search Integration By Solwin is the Magento Extension which will offer you easy integration of Googles CSE into your website.