Custom Search Ads is a Google product that allows publishers who have their own search engine technology to monetize their search results pages.
Custom Search Ads is currently only available to a limited number of publishers. If you think your site may be a good fit, we encourage you to read more and sign up.
If you already use a Programmable Search Engine product, such as AdSense for search, to receive both search results and ads, then you don't need to use Custom Search Ads. All Programmable Search Engines are automatically monetized without any additional steps needed, and you can track revenue earned in your AdSense for search reports.