
Yahoo's PPC platform is branded Yahoo! SEM and has been existed in various forms since 1998, predating google adwords. It was formerly known as goto.com (and then overture) and was one of the first successful PPC advertising platforms in the world for search engines.
Google has come to dominate search which means that many digital marketing agency and marketing manager focuses all their time and effort on Google. This makes the google platform the incredibly competitive, which can diminish the ROI possible. In many instances the Yahoo! auction can provide a much better ROI where shrewd PPC managers are willing to spend the time on learning how this platform performs differently to adwords.