Glossary
Quality Score
Quality Score is Google's rating, from one to ten, of how relevant your advert, keywords and landing page are to what somebody searched.
It matters because it changes what you pay. A higher score means a lower cost per click for the same position, so two advertisers bidding identically can pay very different amounts.
Why it matters to you
It is the reason a small budget spent well can beat a larger one spent carelessly. Improving relevance is cheaper than raising bids and works permanently.
An example
Splitting one advert group covering six services into six tightly-matched groups routinely halves the cost per click, because each advert finally matches the search that triggered it.
Where this comes up: paid advertising .