How do Paid to clicks (PTC) sites make money?

PTC sites make money by charging advertisers to display their ads.

 Paid to click site, act as a middlemen between advertisers and the consumers; the advertisers would pay for the displaying of their advertisements to the ptc admin.;while part of that revenue would autimatically goes to the viewers,whenever, they click and watch the advertisement.

 This is the most known source of paid to click revenue,aside of partnering deals.