Adsense API Mean :
Adsense api is one of the revenue sharing program which mean it can generate revenue for you and for your users by placing ads on your websites.
Eligibility for Adsense API :
Only websites with over 100,000 daily page views across user pages are eligible to participate in the AdSense API program.Otherwise you can monetize with adsense.
Adsense api support :
Where To register site/blog for adsense API :
Log in to your google account and then visit your account page where you can see google code.In google code page select more products under the category featured products.Now you can see the Google Adsense API. or simply visit http://www.code.google.com/apis/adsense