Yahoo! Ads marketing services represents about 14% of the search engine marketing market. Yahoo! Advertising search marketing has a similar approach to that of which Google uses with AdWords, businesses can bid on specific keywords and phrases that are searched on Yahoo!. With a combination of the bid and a quality score depending on click- through rates (the percentage of people that click on the ad), the ad is displayed within the search. Similarly, Yahoo! will also provide advertising on Yahoo! affiliated websites.
Currently Yahoo! ads are handled by Microsoft in their ad center so when you set up Bing pay per click ads you can also set up Yahoo! as well.