The PTC websites will have a community of members(users) like you who work to click and earn money. When advertisers purchase ads, it will be displayed on the PTC sites in the view ads page, where the members can click the ads to earn money. The more ads they click, the more you can earn. This is the process of Online Ad clicking jobs or Pay per click jobs.
or Let's say more Startup project we have for now 5 project they are reall project each project give you good return everyday so of you invest for example :If you invest 10 USD in Ether we will keep 5 USD in our bank and we give the rest money 5 to the (company or the leader of the project )then he work daily . if something going wrong like these project is scam or stop we will ba k to you only 4USD so in these case you did not lose all your money but you lose some part.