If you have signed up to be a google adsense affiliate, when visitors to your page click on an advertisement you will get some money but only when they click on an ad. You do not get paid for visitors in general, though the more visitors you get the more clicks you are likely to get.
If you are an amazon affiliate and/or ebay affiliate when someone buys a product that has come as a direct referral from your hub, you will get revenue. To get amazon and ebay products on your hubs you have to add those capsules in the edit mode.
To sign up to be an affiliate for these companies use these links:
Google Adsense: http://hubpages.com/help/googleadsense
Amazon.com: Read this - http://hubpages.com/help/AmazonAssociates
Sign up here - https://affiliate-program.amazon.com/
If you have already been approved and have added your affliate codes on My Account and then click on affiliate settings you can go form there to see how much you have earnt by clicking check your earnings.
I hope that's clearer.