In a nutshell, when the advertiser creates his campaign in Adwords, he/she provides the keywords that he/she wants the ads to appear for.

Then Adsense tries to match those keywords to the keywords that you are targeting with your content.

However, you can tell Adsense which content on your site you want it to match Adsense ads to, by using what they call "Section Targeting".

Here is the code that you can use to select which part of your content you want Adsense to target:

<!-- google_ad_section_start -->
<!-- google_ad_section_end -->

Conversely, you can also tell Google which parts of your content you want to be ignored. Just use this code:

<!-- google_ad_section_start(weight=ignore) -->
<!-- google_ad_section_end -->

I hope that this helps.

Tony Alves