Abbreviation for Cost-Per-Acquisition, Cost-Per-Sale, or Cost-Per-Lead. CPA is an advertising payment model by which the advertiser pays the publisher (of a website) each time a person clicks on the publislers ad and initiates a Sale, requests a quote (insurance), or signs up for a free trial.
Example: Lets say i'm browsing through your site and on one of the pages, I see a banner that is for a free trial at a dating site, I click on it and sign up for a free profile. That dating site is then going to pay the website owner (Publisher) a agreed upon amount of money.

Abbreviation for Cost-Per-Click. CPC is the agreed upon cost charged to the advertiser by the site’s publisher each time a visitor clicks on the advertiser’s ad (link, banner, etc.).
Example: If a publisher (website owner) charges a fee of $.10 per click then the advertiser would pay $100 for a 1000 click thrus.

Cost per 1,000 impressions (the "M" is latin for 1,000)
The total price paid in a CPM deal is calculated by multiplying the CPM rate by the number of CPM units.
Example: One million impressions at $10 CPM equals a $10,000 total price.
1,000,000 / 1,000 = 1,000 units,
1,000 units X $10 CPM = $10,000 total price

This is the ratio of the number of times and ad is clicked divided by the number of times an ad is viewed. Genrally the higher your CTR the more you can charge for advertisements.
Example:Lets say you have a 100 impressions however you only had 4 clicks, your CTR would be 4%.

A closed ad network is one where there is no direct communication between affiliate and merchant, everything is directed by the network. A merchant offering his website for advertising to a closed network would not know which affiliates are advertising his campaign. An open network is one where merchants can run their own affiliate programs with direct relations to affiliates, the network simply provides the framework for both parties to independently participate in an affiliate program. In an open network, a merchant can decide which affiliates to allow in their program, which campaigns these affiliates can see, recruit his own affiliates, decide what rates they are paid, etc.

The percentage in which the advertiser is willing to pay for the sales generated from the clicks thru the publisher generate. Generally the advertiser pays the percentage for any products and sometimes membership fees paid by your referral.