I think I know what they might be saying. The person who has control of a page or pages) can use Google AdSense to make a little money.
I have several pages like that, on two web sites, on the dedicated LAMP server that we lease. You can see one of them at http://www.w0btu.com/classic_icom.html
That ad is vertical on the right side, and the ads change all the time. They can be horizontal or vertical, big or small. When a visitor clicks on one, then we make a few pennies.
We make about $100 per year from both web sites, IIRC. But I know a guy locally where clicks on the ads on his site pays his monthly home mortgage payment! Here's the AdSense, if you want to sign up: http://www.google.com/adsense/start/
. Those ads are probably on millions of web pages worldwide.
I hope this helps explain things a little.