Hi again Nancy,
There are several differences. If a procedure in a macro module (not an event code module) is declared Private, it cannot be called from any other module. In addition, another module could have a procedure that has the same name, and the two would not conflict: each module would have its own copy of the procedure, and the procedures would not necessarily do the same thing. In addition, a Private procedure will not show up in the list of macros you get when you go to Tools -> Macro -> Macros, so it cannot be run from the Excel interface.
If you declare a procedure as Public in a macro module, it shows up in the Excel interface. In addition, it can be called from within a procedure in any other module in Excel (even other workbooks), INCLUDING the event code modules.
Procedures in macro modules are Public by default (i.e., if declared without the Private or Public keyword), while procedures in event modules are private no matter what.
The same principle applies to declaring variables. A Public variable can be accessed from any code anywhere in Excel, while a Private variable can only be accessed from within the code module it is declared in. Variables are private by default (i.e., if declared without a Public or Private keyword)