Relevance

Relevance is a more abstract idea that isn’t as clearly defined as CTR. However, it is an incredibly important concept for people doing AdWords to understand. If you don’t have a good grasp of relevance, you will always struggle with your AdWords account. Essentially, having good relevance means that everything you do is in alignment. It means that the keywords you set trigger an advertisement that is closely related to those keywords and takes a person to a landing page that is closely related to that advertisement. Google makes an effort to measure this and other factors that concern showing high-quality advertisements in their quality score. It is for this reason that you will never see an advertisement for used cars when you make a search for ski hats. Not to get into a conversation about Google’s rise to prominence as the default search engine, but this stringent control on relevance is a big part of why Google is so frequently used. People like using the search engine because even the paid advertisements are content closely-related to what you are looking for.

Read Google’s definition.