There are two ways to determine the charges for PPC:
PPC Bidding: This is the most used type. In PPC bidding, an amount is specified by the advertiser to go for a bid. The advertiser specifies a maximum amount which he is ready to pay for each time a user clicks on the ad.
Flat rate PPC: it is a predefined charge between the advertiser and the publisher for advertising. The charges may differ from page to page and content to content.