Quality Score – A number assigned by Google to paid ads in a hybrid auction that, together with maximum CPC, determines each ad’s rank and SERP position. Quality Scores reflect an ad’s historical CTR, keyword relevance, landing page relevance, and other factors proprietary to Google. Yahoo! refers to the Quality Score as a Quality Index. And both Google and Yahoo! display 3- or 5-step indicators of quality evaluations for individual advertisers.
Query – The keyword or keyword phrase a searcher enters into a search field, which initiates a search and results in a SERP with organic and paid listings.