A nonsense expression with no real value or purpose other than to act as a catchall for the types of links people think are better than “those other links”. Googlers use “quality links” as a subtle way of telling people to stop getting cheap spammy links. Many SEO forum moderators and admins use “quality links” in a somewhat broader but similar fashion, if only because they don’t know exactly what criteria make links good for any particular search engine but they recognize that people who are asking about linkage have a problem. Nearly everyone else seems to use the expression to refer to their (usually non-performing) backlinks. I wrote about high quality links at SEOmoz (in a post designed to rank for “high quality links” on the basis of content — but the lesson passed over everyone’s head, except for Aaron Pratt who saw what I was doing right away).

A number that is assigned by Google to paid search ads in a hybrid auction that ultimately determines each ad rank and ranking on SERPs. These quality scores will affect the ad's historical CTR, keyword and landing page relevance, as well as several other aspects that Google may take into consideration.

The keyword(s) or keyword phrase(s) that users type into search fields for the purposes of obtaining search engine results. Those results will include both organic and paid search ads.

The collection of all queries and their relevant results for a set of related search expressions.