PCM is the ProCurve Manager application that can be used to manage ProCurve switches from HP. A free version of PCM is available with basic functionality to anyone purchasing ProCurve equipment, and a license can be purchased for a product called PCM+ that provides additional functionality such as traffic and configuration management, policy definition and triggers, etc. PCM+ essentially "unlocks" this extra functionality that integrates into the free version of PCM.
For my $.02 worth, it *would* be pretty convenient to segregate PCM/PCM+ questions in a different forum rather than having to search through all of the device-related questions in this forum ...