Google AdWords Quality Score (QS) is a grading system that helps google and Businesses to analyze the effectiveness of ads.
The 1-10 scale of the Quality Score is influenced by: Expected click-through rate (CTR) and if people click the ad, Ad relevance which is a measure of how closely the ad relates to the targeted keywords, and the landing page experience which is an indicator of how the landing page is likely to perform, and if it’s easy to navigate. A good landing page experience can result in more leads, purchases etc. Determined by Google, the Quality Score can range from 1-10 (where 1 means bad score, and 10 mean great score).
Google AdWords calculates an Ad Rank using the components of Quality Score. This is what determines if and where the ad appears in the paid search results. Higher Quality Scores can translate to better Ad Rank, and higher quality ads usually lead to lower costs and better ad position.