You can define form variables in LiveCycle Designer ES to store specific information in a central, accessible location. A variable typically acts as a placeholder for text that you might have to change in the future. For example, a variable can store the text of a message box title. When the text needs to change, all you have to do is open the affected form or template and update the text once through the variable definition. LiveCycle Designer ES automatically propagates the new text across all instances of the inserted variable.
Keep in mind that form variables are defined outside of the Script Editor, and are accessible by scripts on all objects on a form, as opposed to scripting variables that you create in a specific FormCalc or JavaScript script.
You can create, view, and delete variables without using scripting. However, you must use scripting to access the values stored by variables and manipulate them, or to apply the values to objects on your form.
See also 

About variables