what do you mean by quality score?

A diagnostic tool called Quality Score is designed to help you gauge how well your ads stack up against those of other advertisers. This rating, which ranges from 1 to 10, is available at the keyword level.

To assist you assess how your advertising compare to those of other advertisers, a diagnostic tool called Quality Score is available. At the keyword level, you can access this rating, which runs from 1 to 10