If you are getting into macros then you need to know about programming in Visual Basic for Applications (VBA) and with that you need to know about variables.
VBA is a great tool for automating so many tasks in Microsoft Office and can seriously speed up how you work and also help reduce errors too.
Variables store information that can be used later in a program whether it be VBA or another programming language and you need to know how they work. The store information such as numbers, dates, strings (text) and objects.
Here is a video tutorial that shows you more and also has an example using Excel, although the applies to all of the Office programs.