Here is some definition:
CPM - cost per impression
Every time an ad is displayed it counts as one impression. Rates are usually quoted for 1,000 impressions. Good choice for a busy site.
CPC - cost per click
Every time someone clicks, it counts as one clickthrough. Rates can be anywhere form a cent to a dollar with .10 to .17 being common.
Leads
If you send a person to the site who then "signs" up or participates in some way specified by the ad sponsor then a "lead" is created.
Sales
You receive a commission on sales. Amazon is an example of this type of program.
Affiliate
When you join up with a program or "associate" yourself with it you are an "affiliate". Usually they handle getting the ads, keeping statistics and you just need to display the ads.
Enjoy making money from your site
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