The items are the central object in any PLM system - only those elements can be used to create, maintain etc. a product which are managed as items in the Item Management module. An item represents any part of a product - a single screw, an assembly or a complete machine.
At the beginning, any item is an individual item without any structure or referenced information. By relating items and grouping them hierarchically, so-called Bill of Materials are defined (related items). Bill of Materials structure a product from top level (= product e.g. ball pen), across the individual assemblies ( e.g. clip) down to the level of the individual item (clip ring etc.).
As the item is the central object of the PLM system, references to other objects of the PLM system like documents, projects, files, companies and persons etc. are possible and give additional information about the specific item.
Like most objects in the system, the item is under version-control - meaning that different revision states of an object can be tracked. To show all information referenced to an item without considering the status, the Item Master is created. The item master shows all information related to the item independent of the item revision.