Provisioning is a term that is familiar to service providers (a.k.a. operators, a.k.a. telephone companies) and OSS systems but not so much in the non OSS enterprises.
Provisiond receives "requests" for adding managed entities via 2 basic mechanisms, the OpenNMS HORIZON traditional "New Suspect" event, typically via the Discovery daemon, and the import requisition (XML definition of node entities) typically via the Provisioning Groups UI. If you are familiar with all previous releases of OpenNMS, you will recognize the New Suspect Event based Discovery to be what was previously the Capsd component of the auto discovery behavior. You will also recognize the import requisition to be of the Model Importer component of OpenNMS. Provisiond now unifies these two separate components into a massively parallel advanced policy based provisioning service.