One of the keys to combining targeting is to help advertisers reach specific audiences or demographic groups. Here's how Ad Manager handles multiple targeting conditions.
If you specify multiple values under a single targeting type (such as browser or device category), Ad Manager joins them using an "OR". For example, if you select "Safari" and "Firefox" as browsers you want to target, Ad Manager targets site visitors using Safari OR Firefox. You'll reach both audiences, those using Safari and those using Firefox.
Targeting between targeting types is handles as an "AND". For instance, suppose you wanted to reach an audience that was in North America using only Firefox browsers. Under Geography, you might target "United States" and "Canada"—there would be an "OR relationship between these two as they are values under the same type. Now, under Browsers, your target "Firefox". You'll reach an audience only if they are deemed to be in the United States or Canada and using the Firefox browser.
Targeting values can also be hierarchical or flat and behave differently when you add them to the targeting picker. Learn more.