Simple basic about a PTC site?

A PTC site is a website that pays users to view ads and complete other tasks. Any other idea, please share

 That is the only central idea behind the paid to click site ; only that you talk partly just regarding the consumers side or rather ,the participants who aim to just do the task and earn some money , otherwise,some are advertisers who brough the contract to the paid to click site and their sole aim there is to draw traffics to themselves and being known in the business.