Dynamic keyword insertion Wikipedia
Dynamic keyword insertion is a feature provided by Google Adwords, Microsoft adCenter and Yahoo! Search Marketing to dynamically insert a keyword that is most relevant to the ad to be displayed. It helps advertisers to use relevant keywords on their ads while making it easier for them to create unique ads for a large number of keywords.
One user searches for "north carolina car insurance" and a second user searches for "maine car insurance." An advertiser bidding on car insurance keywords in both states can use dynamic keyword insertion to insert the user's state on-the-fly. (see image to the right)