why on some sites ? there are adsense ads linking to the same site we are on ?
 

lets say,

i am on stackoverflow and i see adsense ad on it. and i click on that ad, but it does not take s me to another site , its linkting to acutal content on stackoverflow itself , why is that ?

i mean why would i pay google via adwords to place ad on my site and make money via adsense when user clicks on it ?, i would be loosing money here .

so what are those links/ads ?

thanks for your time.

Possibly filler for unsold inventory.