A package is a file containing code or a code library in some format. In a library rule or function rule, you can import external Java packages (Rule-Utility-Library and Rule-Utility-Function rule types).
By analogy, the first key part of most PRPC service rules (Rule-Service-COM, Rule-Service-SOAP and others) is known as a Customer Package Name, or simply a service package. Packages — the set of rules that share this first key part — are the unit of compilation and interface file creation.
Values for the Customer Package Name are defined in a service package data instance (Data-Admin-ServicePackage class).
For the PegaRULES Process Simulator, a flow package is an instance of Rule-Simulator-FlowPackage rule type.