What is a Procedure Signature?

A procedure signature is the declaration line of a Sub, Function, or Property.

It includes the following parts:

Scope: Public, Private, or Friend
Procedure Type: Sub, Function, or Property Let/Get/Set
Identifier: i.e., the name of the procedure
Parameter/Argument List: a comma-delimited list of parameters that appear within parentheses after the procedure name
Return Type: follows the As keyword; only applies to Function and Property Get procedure types

Signatures are how your calling code interacts with your procedures.

Be careful changing procedure signatures to avoid breaking backward compatibility with the rest of your code base.