Quality Score is an estimate of the quality of your ads, keywords, and landing pages. Higher quality ads can lead to lower prices and better ad positions.

• You can see your Quality Score (Quality Score is reported on a 1-10 scale and its components (expected clickthrough rate, ad relevance, and landing page experience) in your keywords’ “Status” column.
• The more relevant your ads and landing pages are to the user, the more likely it is that you'll see higher Quality Scores.
• Quality Score is an aggregated estimate of your overall performance in ad auctions, and is not used at auction time to determine Ad Rank.

* Nguồn: Google