The variable assignment is the value used by a variable. The value is used in the published output, or when the variable is used to assign metadata.
Any variable used by an object can have a new, or different, value assigned to it. For instance, if you wish to set a variable value for a specific book, you can assign a new value to the book object that will replace the default library value, and in turn, alter all occurrences of the variable in the book. Alternatively, you can nominate specific topics to be assigned a new variable value, while the rest of the book uses the default variable value.