Assuming that you control your website- you have total control of which pages will get the Adsense ads. YOU put the adsense code (a block of Javascript) on the site. On the other hand, if you don't control your site...maybe you use a blog system...the ads will probably appear on every page. So like most things, if you do the work, you get the control. If you don't do the work, then you lose the control.
Read google's TOS and you will see. But mostly, user friendly stuff should do Hopes this helps, -Steven
Hey buddy, ads only come when you put the Javascript code for that. So, put the codes in the pages you wish to see and dont put code in pages where you dont wanna advertise..thats all