Initially it seems that the pay per click is a simple one type program while it is not. There are several types of PPC programs that include comparison PPC, service PPC, Pay per call PPC and Pay Per delivery PPC.  

Service engines allow the providers to come up with feeds of their service databases. When the user starts his search for a service or product, the service engine provides the link to the required web page. The Service PPC often gives priority to the advertisers who pay more. But users still have the option to sort the displayed items by prices in ascending order starting from the lowest one. Thus the vital part of it, the pay per click management becomes quite easier for you with things automated in the process. Some of the PPC’s have also expanded their operational area. Some notable PPC service providers are NexTage, SideStep, and TripAdvisor. 

Just like the pay per click, there is another system called pay per call. This is a business model that is used for ad listings in search engines and directories. This allows the publisher to charge the local advertisers on a per-call basis. However, when you are dealing with Website design please do not confuse pay per call with the click to call which is a different method altogether. In fact, click to call with call tracking facilities constitute the pay per click system.