A variable holds a specific value type in the workflow process. For example, you can insert a variable in an activity containing a message to indicate the resulting value of the variable.
Note: A variable is used internally and is not visible to users when the workflow runs.
You can define the following types of variable:
Open the properties of the workflow that you want to add a variable for.
On the Variables tab, click Add.
The Add workflow variable dialog box appears.
In the Name box, enter a name for the input.
In the Value box, enter a value for the variable
From the Type list, select a variable type, such as string.
To store all processed values in a list, move the Is list toggle key to the right.