When a paid advertisement appears on a SERP, the possibility exists that an internet searcher may well click on that advertisement. The CTR is the amount of times an internet user clicks on the advertisement in comparison to the amount of times the search engine displays the advertisement. For example, if Google shows an advertisement 100 times in a month and out of those 100 times, 25 internet users actually click on the advertisement, then the CTR is 25%. The higher the CTR, the better the advertising campaign actually is because it affects quality score.