At it’s core, a provisioning server is a type of server that sends configuration data to devices that request it. That configuration data is commonly found in the form of XML files, plain-text files, or even binary files. The type of file depends on the device requesting the information.
A provisioning server receives requests for configuration information from devices during the setup/bootup process or on a regular basis. A provisioning server allows service providers to tweak settings and choose the optimal configuration for their customers devices.
Provisioning servers are used to assign configuration to all types of devices, including phones, routers, cable modems, and wireless devices
However, they are most commonly used to manage and deliver configuration to VoIP phones. This becomes useful when deploying a large number of VoIP devices at one time.