CTR is the most heavily weighted component of quality score. Google looks to CTR as a means of getting users’ feedback on ad text. If an ad has a high clickthrough rate, this must mean that many users are finding it relevant and useful to what they’re looking for.
Relevancy is the second largest component. Google takes into account the relevancy of a keyword to an ad as well as to the user’s search query. Relevancy is Google’s way to display only useful ads to users. It also prevents advertisers from simply buying their way into an ad auction, when their product or service is irrelevant to the search.
Landing Page Quality is the third component of quality score. In Google’s opinion, a landing page that is high quality contains relevant, original content, is easily navigable, and has quick load times, with minimum pop ups. It should also be completely transparent about the nature of your business, how your site interacts with the visitor’s computer, and how you intend to use the visitors’ personal information.