In general terms of parameters in WF4.5, there are three main concepts: Variables, Arguments and Expressions. The definitions for each are that Variables are used to store data within a workflow workflow, Arguments are used to passing data and Expressions are used for manipulating data inside a workflow. In workflow Designer panel there is a custom panel for Variables, Arguments and Imports. 
Variables
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To define a new variable, click on "Create variable" row and choose proper values for "Variable Type", "Scope" and "Default" columns.
Arguments
Arguments are used to define the flow of data in and out of a specific activity. Arguments may be: In, Out, In / Out or Property. When building a workflow workflow, arguments are defined to allow data to be passed into the workflow workflow when it is executed outside Designer Basic (for example, Flowster Studio - Portal) . The arguments are defined in the same manner as variables in workflow Designer->Arguments panel.
If the workflow has predefined arguments, they will be visible in the Arguments panel. In order to edit existent arguments, click on the correspondent argument row and perform desired editing.
To define a new argument, click on "Create argument" row and choose proper values for "Direction", "Argument Type" and "Default values" columns.
An existing variable/argument can be bound to a property of an activity by clicking the button (Quick Binding). A list with all defined variables/arguments will be displayed:
In order to filter the list of displayed variables/arguments by matching type (e.g. if a property is of type <Int32>, only variables and arguments of the same type should be displayed in the list of variables/arguments from Quick Binding), go to Settings and set the Quick Binding Filter to ON:
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