Custom Search Engine (CSE)
A Custom Search Engine, often referred to simply as a search engine, is a tailored search experience that allows you provide customized search to your website's users. With a Custom Search Engine, you can customize the appearance of the search box and search results that you display on your site. You can also refine the search results to make it easier for your users to find the information they're looking for on your site.
AdSense for search allows you to create a Custom Search Engine and earn by displaying AdSense ads on the search results pages.