This can be a little confusing, because in each case, your advertisements are placed on other sites to be seen by people who may be visiting those sites. However…
Pay Per Click (a.k.a. Cost Per Click)
In pay per click advertising, the ad appears on the chosen website for all visitors to see and many people will see it, but will not click on it. In other words, they will read your ad but will move on without clicking on the ad to visit your website and/or to gain more information. But as soon as someone does click on the ad, then the advertiser is charged an agreed amount – usually just a few cents. Whilst you can get some free exposure if a reader does not actually click on your ad, this may not have a lot of value in that probably the viewer does not have a great deal of interest in the subject of your ad. The cost per click that will be paid is agreed between the two parties before the advertiser submits his ad to be placed on the receiving website.
Pay Per Impression (a.k.a. Cost Per Mille)
An impression is in effect the appearing of your ad on the host’s web page when someone visits that page. Each time that the page bearing your ad is visited, that visit counts as one impression. You are paying for the fact that someone has visited the page bearing your ad, irrespective of whether or not the visitor clicks on your ad, and irrespective of whether or not the visitor has even seen your ad. Pricing usually is agreed at a rate per 1,000 impressions – hence cost per mille. So, in summary, you are paying an agreed fee for your advertisement to appear before each batch of 1,000 visitors, irrespective of whether or not they see your ad or click on it.
