When you place an AdSense for search box on your site, you can improve your users' online experience while generating a new revenue stream. Your users will benefit from targeted search results from your site and the web, and you’ll generate earnings for valid clicks on the ads which appear on search results pages.
In addition, you can take advantage of advanced customization options like vertical search and keyword tuning to improve the relevance of your search results and ads. Don’t want users to leave your site after performing a search? Try the SiteSearch only feature to deliver results only from your own site.
More information can be found in the AdSense for search section of Google Help Center. If you’re already using AdSense for search on your sites, review our optimization tips for ways to improve your search revenue.