VBA (Visual Basic for Applications) is a programming language for developing macros and custom functions in Microsoft Office applications like Excel. The document discusses how to enable the developer tab, insert a command button, write VBA code to add functionality like message boxes and input boxes. It also covers various VBA concepts like variables, constants, operators, conditional statements, loops, functions, and sub procedures. Examples are provided to demonstrate how to use these concepts to manipulate data and add interactivity using buttons in Excel.