This is Jonathan from Kontera. The way Kontera works is, as cpvr says, we place ads over your content, which appear when your readers scroll over the highlighted word. You can implement Kontera on your Hubs, by signing up as a publisher on Kontera's website, and then by entering your Kontera publisher ID number on your HubPages Affiliate page.
Just to clarify our payout terms, our minimum payout threshold is $50, if you earn anything less than that, your earnings just roll over into the next month until you do reach $50.
- Jonathan Cohen
Kontera Community Manager