How does it function?

Handling PIDs is very simple. First you need to register a for a resource or service. You can do this very simply by providing the required information to the PID service site, in particular the path to access the resource such as a URL and you will receive back a PID which you can enter into the metadata description for example, so that everyone can use it for referencing. When a user finds such a PID in a resource, he/she can click on this reference and the service will resolve the PID and give access to (one of the copies of) the resource. Normally as user you don't see the intermediate transactions.