Contextual targeting allows you to advertise to users based on the content they search in the different search engines.
Whenever an impression comes into the system, the URL of the impression is analyzed. Once the content of the URL is evaluated, it returns with several categorizations.
With the use of this data, we know the topics/categories that any URL falls in, before you bid on it. If a page does not meet your criteria you determined, the system will not bid on it.
Optimization:
Since we currently do not offer specific statistics for contextual targeting campaigns, we recommend running campaigns with only one (or a few) contextual category targets. The reason is to isolate which contextual categories are working and which are not.
So for easier optimization, make a new campaign for each contextual category you plan to target, or, group similar contextual categories together.
For example:
Automotive > Performance Vehicles
Automotive > Vintage Cars
Automotive > Car Culture
could all be grouped into a single campaign as they all relate to automotive enthusiasts.