Pay per click. An online advertising model used by search engines , web directories and web sites. The advertiser only pays when some one clicks on an advert, this enables the advertisier to keep a tight reign on their monthly budgets. For example if I were to search on Google for seo company I would get a selection of PPC ads on the right hand side of the web page - if I were then to click an ad the advertiser would have to pay an agreed amount (you set the maximum you are willing to pay) to Google which is also known as CPC (cost per click). By advertising in this way it ensures that the traffic you get to your site is qualified and tracked.