Intent matters to many advertisers
But developing new ways to find those who are active shoppers or researchers can be challenging in a competitive marketplace. Google Adwords for years has provided the best means to serve Ads to people actively searches for a product, service, or anything an advertiser wants to convey. Choose your keywords, develop your Ads, bid on those keywords, and hit go. But those same shoppers only spend a maximum of 1 minute on Google or Bing.
Search Retargeting allows you to speak to those same searchers, everywhere they go around the web.