Project vs. Temporary macros

[tan125]

What is the difference between a project macro and a temporary macro? Temp macros are specific to the instance of VBP, but I guess what I'm asking is what defines the scope of a project for a project macro? If I have a project macro, and I have a step where I call a different .bld file, do I need to pass it into that .bld file or is this considered within the scope of the project?