Google AdSense crawler crawls your website and tries to extract keywords from your pages. While Google generally performs the task well, you can help them to do it better. This is because certain part of your site is not always related to the content of the page. This normally includes the sidebar, footer, and sometimes maybe the comment section if you're running a blog.
Section targeting will help Google AdSense to serve ads more relevant to your site's content, which normally means higher click-through rate (CTR) thus increasing your AdSense income.
Section targeting allow us to emphasize specific part or section of our page for Google AdSense. To implement it, you need to add some HTML tag to mark the start and the end of the section that yo want to emphasize.
Here's the HTML tag to emphasize a page section:
<!-- google_ad_section_start --> ....... <!-- google_ad_section_end -->
You can also specify a section of our page to be ignored. This is normally applied to the sidebar and the footer section of the page.
<!-- google_ad_section_start(weight=ignore) --> ....... <!-- google_ad_section_end -->