Search advertising is advertising on the results pages of search engines where an advertiser typically pays for each click on an advert. These adverts consist of text, links and Ad Extensions. They are listed above and alongside the organic search results, and are marked as adverts so that users are aware that these are paid-for listings.
Search advertising is targeted according to keywords, demographics, behaviour or interest. On search engines, the CPC is determined by an auction.
The success of an advert may be determined by its CTR, but the success of a campaign will be determined by its conversion rate and its ability to achieve a target CPA. After all, it’s not enough for users just to click on your adverts, you want them to take specific actions on your site once they get there.