Until now, Google's ad settings page had 2 sections for interest-based ads on Google sites and non-Google sites. Google changed this: there are now separate pages for signed-in ads and signed-out ads. When you are signed in to a Google account, Google can use data associated with your account: Google search history, YouTube history, Google+ profile, manually added interests and more.
The section for signed-out ads has 2 separate settings for "ads based on your interests on websites beyond google.com" and "Google Search Ads based on your interests". Google uses your previous searches and browsing history to improve search ads, but you can disable this feature. AdSense ads also use your browsing history and anonymous demographic details to improve ads. Signed-out ads rely on cookies tied to anonymous data.
"You can control the ads that are delivered to you based on anonymous information by editing these settings. These ads will more likely be useful and relevant to you and your Google services, such as search," informs Google.
Google's help center has more information. "To opt out of all of Google’s interest-based ads on your browser, you'll need to opt out in 3 places: once when you're signed in to Google products, once when you're signed out, and once for ads on the Display Network ('websites beyond google.com'). The reason for the different opt-outs is that Google uses different information to target ads, depending on how you're interacting with Google and whether you're signed in with your Google account."
{ Thanks, Herin Maru. }
