CPA / Cost Per Action – Same as CPL/PPL – Advertiser only pays when a desired action is achieved (sometimes called cost per acquisition).

CPC / Cost Per Click – Same as PPC – Advertiser only pays when their ad is clicked upon, giving them a site visitor.

CPL / Cost Per Lead – Same as CPA - Defined as the successful completion of the advertisers Lead form (hosted on advertiser’s or publisher’s site).

CPM / Cost Per 1000 Impressions – Advertiser pays every time 1000 impressions of their ad are shown.

CTR / Click Through Ratio – The percent of impressions of an ad that are clicked on. CTR = # of Clicks / # of Impressions

SEO / Search Engine Optimization – Getting your web pages listed for free on search engines like Google, Yahoo, MSN, Ask Jeeves. This does not include paid listings.

SEM / Search Engine Marketing – Any marketing using search engines, including SEO, PPC, Paid Inclusion – sometimes SEO is considered a separate entity (because there is no direct cost per visitor)

PPC / Pay Per Click – Same as CPC, however, this often refers to bidding on listings on PPC search engines like Overture.

PPL / Pay Per Lead – Same as CPL

ROI / Return on Investment – A calculation of the amount of profit generated by an expenditure. ROI is used as a metric to help managers effectively spend resources. ROI = (Revenue-Cost)/Cost or ROI = (Revenue/Cost)-1