Revenue is generated by the advertisements on our individual articles. All of the ads are based on the article content (by keyword). When a reader clicks on an ad, the advertiser is charged this is called, pay per click or PPC. Google (or whoever is providing the advertising for the site) then gives a share of this advertising revenue to the site owner (eHow, Suite, Infobarrel, etc...), who in turn shares it with the authors.
Occasionally, there is a ad that shows up on your article that is pay-per-view or PPV. Revenue is then generated every time your page is accessed and viewed. This amount is usually pennies in comparison to PPC ads, but is nice none the less.
How do they determine what my share is?
No one knows exactly how revenue is calculated, such as what percent goes to whom etc... it is all a big secret. It is believed that to many people would figure out the algorithm and cheat the system, so it is top-secret.
Can't I just have my friends and relatives click on the ads?
No you do not want to do this. Each time an advertisement is clicked the unique IP address is recorded as a check/balance for the advertisers. When the system detects an individual IP address clicking on ads over and over, it will throw out all that computers "clicks", none of them will count. They will not charge their customer and will not pay you.
This is also a major rule violation, called click fraud. Click fraud will get your Google account closed, your articles removed and account closed at most contribution sights.
Different Sites, Different Revenue Set-Up and TOS
Each site is different and each site has a different way of calculating your revenue. Be sure to read the TOS or terms of service for each site you submit your articles to. This will educate you not only on how you are paid but what is expected of you as a contributor.
It is best to concentrate your efforts on providing keyword rich, quality content.