Have you seen search box containing text google custom search? This search box is called Google custom search box.Here is the short tutorial on how to add Google custom search box to your website before that I am going to tell you the advantage of Google custom search box. When someone searches for your site in custom search, the result will come along with some ads, this is AdSense ads you know very well what happened when someone clicks that ads.
Open Google Adsense and sign in.
Click on my ads tab, from left sidebar you will see search, click on that.
Click on New custom search engine