Google Quality Score

Google Quality Scores reflect Landing Page Content relevance to Keywords.

Quality Score Factors are:

Click Through Rate of the Keyword and Matched Ad
Click Through Rate of the Entire Account
Account Performance in the Geographically Area the Ad is Shown
Keyword Relevance with Respect The Entire Ad Group
Landing Page Quality and Relevance (Essentially, On-page "SEO" for that Keyword)
Ad Copy-Keyword Congruence
Secret Stuff Google Won't Tell Us

Google Adwords

Google displays good Quality Score advertisements more frequently and/or in higher positions. More Click-Throughs to your web site and lower PPC per-unit costs result. Your ads rank is determined by your Bid and your Quality Score. Therefore, Higher Quality Score = Better Placement at the Same Cost

Quality Scores help Google display PPC ads linking to relevant, useful landing pages. Google wants customers to find their PPC ads relevant and useful. Advertisers and Google have shared interest in PPC ads that are relevant to search terms.

By using multiple Campaigns, Ad Groups, Ads, and Landing Pages, you can help create specific Ads and Landing Pages that are very relevant for specific keywords

Keyword: Littleton Pizza Delivery

Google Adwords Ad:

Fred's Pizza Littleton CO
Hot, Tasty Pizza Delivered Fast
Littleton's Best Pizza for 8 Years

Website Code:

Title Element: Littleton Pizza Delivery | Colorado's Best Tasting Pizza | Fast Delivery

Description MetaTag: Fred's Delivery Amazing Pizza to all of Littleton, CO. With 110 Pizza Varieties Available for Delivery, You'll Enjoy a Hot, Fresh Pizza in Minutes

Main Page Header (H1): Fred's - Littleton's Best Delivered Pizza

First Sentence of Page Text: Fred's delivers pizza to all of Littleton: If you are in the city limits, you are in our delivery area!

Image Alternative Content:"Picture of Pepperoni Pizza"

In this example, there's consistency: The Ad, Title, Description, Header, Content and Images all are relevant to the search term.

Here's good practical example (note: emphasis is mine for clarity) from 2012: I searched "Night Skiing Keystone"

A Google Adwords Ad was served at the top of the page, with:

Night Skiing at Keystone |

Keep Skiing Into The Night at Keystone - Book Your Trip Now!

Night Skiing in Colorado |

See the Rocky Mountains in an entirely new light with night skiing at Keystone. You can ski, ride or session at A51 Terrain Park long after all the other mountains close. Learn about Keystone night skiing here.

"Night skiing" and Keystone appeared several times in the content of the page as text or alternative content