Essentially you define a rectangle in your app which will eventually contain an advert. You control when the rectangle is visible or not, and where it should appear. You sign up with one or more advertising companies and obtain your unique AD ID and other particulars, which you feed into the AppGameKit commands as advertising details. When your app goes live, those advert exposures equate to click-through from users of your app, and the company who runs the advertising gives you cash for putting their ad in your app. If you published through TGC, we would place a percentage of adverts of our own into the same space equal to the percentage of the royalty rate of the app income, so advertising revenue from your apps goes directly to you, and the adverts TGC serve through the same space goes directly to us, keeping the finances simple.
I drink tea, and in my spare time I write software.