The terms cost-per-click (CPC) and pay-per-click (PPC) are frequently used interchangeably, however occasionally they are used in reference to separate defined terms. When applied independently of one another, CPC is the sum paid by an advertiser to search engines and other Internet publishers for a single click on their advertisement, which directs one visitor to the advertiser’s website.

Pay per click (PPC) is applied online where advertisers pay their host only when the ad is clicked. With search engines, advertisers typically bid on keyword phrases relevant to their target market.

Content sites commonly charge a fixed price per click rather than use a bidding system.

See also:
Cost per acquisition/action (CPA)
Cost per thousand
Affiliate marketing
Conversion rate
Reciprocal links
Ad rotation
Ad impression
Behavioural Targeting
Contextual Marketing
RSS
E-Marketing
User Session
Deep Linking