Impressions are views. HubPages put your AdSense code on the ads 60 times out of 100 and their own code on the ads 40 times out of 100. If someone clicks when your code is on the ads, you get 100% and vice versa. The amount varies depending on how much the advertiser is paying, keywords, etc.
Some Google AdSense advertisers do pay for impressions. However, it's usually not that much. Sometimes only a few cents per 1000 views.