HubPages is a revenue sharing site. They have an AdSense account. The ads appearing on your hubs has their AdSense affiliate code on them. If your visitors click the ads, then HubPages gets all the earnings.
If and when you're approved by Google and have your AdSense code set up in your HubPages settings, your AdSense affiliate code will be on the ads 60% of the time and HubPages' will appear 40% of the time. If visitors click on ads that has your affiliate code then you get the earnings. If HubPages' code is on the ads, then they get the earnings.