A macro is a reusable part of a business rule that can be referenced by other business rules and macros to save you time when you are writing business rules and sequences. Macros are global so you can reference them in business rules or another macro. Macros can contain variables and other macros, but they cannot contain themselves.
For example, you might want to create an initialization block macro for the beginning of your business rule that you name %stdinit instead of set updatecalc On; or set aggmissg Off;.