New to WF and have a question

Hello everybody. I've been involved in IM'ing for about 3.5 years. I've built about a dozen websites and have really only had success with one of them. It's a site where I promote some different ebooks/informational products that I personally wrote and sell in my online store.

Now I would like to go in a slightly different direction and have a question.

What would the type of network be called that offers an ad management network, where the company offers a script or plugin you put on your website, and an advertiser visits your website and can sign up right there thru the script/empty ad box that is displayed on your page? I know that question is a bit vague/unruly, but there is a company OIO publisher that has something very similar to what I am asking about. What type of ad network would they be considered to be?

Also, is there others out there similar to OIO? i'm new to this form of advertising. Adbrite was sort of similar back in the day, but not quite the same as what OIO looks like.

Anyways, thank you for any help/suggestions. Time to read some more threads on WF!

Josh