The use of a site visitor’s search history as a basis for the ads that the visitor will see.
Search retargeting lets advertisers reach out to untapped markets by using a visitor’s search history to predict his or her interests. For example, suppose a search engine user regularly searches for terms like “clean”, “energy” and “environment” for a couple of hours. With this data, ad providers like Google AdWords or Yahoo! Marketing can serve ads about sustainable living and environmental protection.
Search retargeting is one way to expand the messaging opportunities in niche markets. Individual keyword searches only exist for a moment, but the people behind the them continue to exist and, in many cases, maintain an interested in the topic. Of course, it’s difficult to duplicate the effectiveness of the original searches that reach people at the height of their intent, but search retargeting has the potential to add a degree of search-like value to less valuable non-search inventory.
see also: Online Advertising Tools