Quality score is a metric recorded in Google AdWords and Bing Ads reporting the combined relevance and historical performance of your ads, keywords, and landing pages in regards to a user’s search query.
Quality Score can also be a helpful warning signal when there are particular ad groups or campaigns in a PPC account that need to be optimized- typically, the better your Quality Score is, the better your ads perform. Both Google AdWords and Bing Ads score each keyword on a 1 through 10 ranking scale with a score of ten representing the best QS a keyword can obtain.