A little online ad terminology

Quote :

ad impression: Each time someone views an advertisement online.

ad networks: A company that sells ad inventory in aggregated packages to advertisers. One example of an ad network for blogs is called BlogAds.

banner ad: Graphical advertisement on a web page that allows people to click through to a special advertiser’s site.

behavorial ads: Advertising that’s served up according to a person’s recent online web surfing, matching their interest even if they are not currently on a relevant site.

clickthrough rates (CTR): The percentage of times that a person seeing an ad online clicks on the ad.

cost per action (CPA): A type of ad in which the advertiser only pays the publisher for each time someone completes a transaction, whether that’s registering for a site or buying a product.

cost per thousand (CPM): The rate it costs for the ad to reach a certain number of viewers online. So a site with a $10 CPM would charge $100 for every 10,000 viewers reached.

pay-per-click (PPC): An ad in which the advertiser only pays for each click made by viewers, with the price set by bidding against other advertisers online.

opt-in marketing: Ads or commercial emails sent with the prior approval of recipients.

rich media ads: Display ads online that use animation, flashy graphics, audio or video to pop off the page for viewers.

spam: Commercial email messages sent without the recipient’s approval.

Taken from MediaShift's pretty comprehensive enty about online advertising.