A persistent identifier (PID) is a long-lasting reference to a resource. That resource might be a publication, dataset or person. Equally it could be a scientific sample, funding body, set of geographical coordinates, unpublished report or piece of software. Whatever it is, the primary purpose of the PID is to provide the information required to reliably identify, verify and locate it. A PID may be connected to a set of metadata describing an item rather than to the item itself.
There are different PID types for different kinds of resources. In the current research environment we most commonly see two varieties: those for objects (publications, data, software, such as URNs, DOIs, ARKs, Handle) and those for people (researchers, authors, contributors, such as ORCIDs, ISNIs). Many repositories will assign a PID of the former type when an object is deposited.
For more information, please see the Knowledge Hub on the PID Forum.