Promotion Level (or group) refers to a modules status in the software development lifecycle, most often as defined as part of an overall software configuration management (SCM) strategy.  A very simple software development lifecycle:


The lifecycle is often implemented within a SCM tool, such as StarTeam, PVCS, ClearCase, or MKS.  It is often (and should be always), part of a larger SCM plan, including workflow, release management, issue management, and other considerations.  SCM is often implemented in an effort to achieve a Capability Maturity Model ranking/certification.