There are two types of Variables: Custom and System. Variables may be referenced in PDQ Deploy Packages.
The following package fields will expand variables:
Command Step
Command, Additional File
Package Step
Parameters, Install File, Additional Files
Reboot Step
Message
Custom
A PDQ Deploy user can create, delete and modify Custom Variables. Custom Variables can be referenced using the @(...) convention.
System
System Variables cannot be modified but can be referenced using the $(...) convention. (Note: the $(Repository) system variable may be modified in the Repository window)