These types of ads are characterized by redirecting the user to another website where some task must be completed. After the user completes the given task, the website will post back to the GPT website telling if the task has been successfully completed or not. The GPT software will, then, credit the user accordingly. Postback based ads include PTSU, PTRV, PTTS, PTCO and PTX.
Two fundamental concepts here are subid and postback.
Subid is a unique value that forms the target URL link and is used by the external website (ad network) to uniquely identify what user completed what ad. Subid variables are included in the postback URL in the form of macros that the GPT software will automatically parse and replace with the unique identifier. Other variables (in the form of macros or not) may be eventually required to be included in the target URL as well. The exact way a target URL should be formatted will be documented by the ad network.
The postback is a HTTP post (in GET or POST format) that the ad network will send to the GPT website after the user has completed the task. It will include variables that can be used to determine whenever the user has properly completed the task. The base of the postback URL will be the GPT listener. GPTEngine includes a listener for each type of ad. For instance, for PTCO campaigns, the listener URL is http://yourwebsite/ptco.pb. For PTSU, it is http://yourwebsite/ptsu.pb and so on. The final URL will be formatted according to the specifications provided by each ad network.
PTSU, PTRV, PTTS and PTCO campaigns are technically the same the only difference, in name, being designed to keep your GPT campaigns grouped by the type of task to be completed.
PTX (generic GPT) campaigns are basically the same as the above types, the major difference being that they include the categories features so one can easily group custom types of tasks and the recurrence feature that, if enabled, allows a campaign to be completed more than once by a user.