The most important advertising industry definitions:

• A click or click through is defined as a mouse click on banner or textlink ads.
• A raw click is definded as a click from any IP address.
  A surfer may click the same banner twice and both clicks are counted.
• A unique click is defined as a click from a unique IP address, per banner, within a 24 hours period.
• An impression is defined as an ad view.
  Sometimes the ad has to be viewed a specific period of time to be counted as an impression.
• An action is defined as a sign up, filled out form, purchase or even click.
• CPM - Cost (or payout) per thousand impressions
• CPC - Cost (or payout) per click through
• CPA - Cost (or payout) per action