CPC stands for Cost per Click. That means, you will be charged per click. Many famous advertising networks like Google AdWords, Facebook Ads offers purchase of their traffic on CPC basis too.
Suppose, you are having a website and you want to get visitors (traffic) to your website. For that, you can create some ads and purchase ad slots in other websites and place your banners ads in other websites. So, that people from those websites will see your ad and click on it and come to your website through that banner ad.
But, mostly many websites uses Google AdWords or advertising networks for displaying ads in their websites. So, in order to display an ad, in the site which is using AdWords, you need to purchase ads from Google AdWords. And Google AdWords offers two type of options to buy traffic or visitors from it.
So, if you bought a banner ad from Google AdWords on CPC basis, that means, you will be charged by Google whenever your ad got clicked by other people.
Say like, the CPC is $2.
That means, for 100 clicks, you will be charged with $200.
Unlike CPM, you will never be charged for the number of impressions your ad will receive. Suppose, if you receive two million impressions and only 2 clicks, you will be charged with $4 only (considering $2 CPC)
Here is an example:
$1 CPC – 105000 Impressions –100 Clicks – you will be charged $100 (Only for Clicks)
$0.50 CPC – 104393839 Impressions – 28 Clicks – you will be charged $0.50×28= $14 only for clicks.
$0.30 CPC – 90043 Impressions – 248 Clicks – you will be charged $0.30×248 Clicks = $74.4 only for clicks.
In the above, regardless of the number of impressions you received, you will be charged only for clicks.
Here is the list of some of the advertising networks which offer their inventory on CPC basis.