Value binds a component to the variable selected. For example, if you bind a text input component to a variable, the input box will always display the value of that variable, ignoring any placeholder text specified. The variable is automatically updated with text typed by the user, subject to validation processing.
Other controls, radio buttons for example, use Value with a Selected Value Text setting. When the radio button is selected at runtime, its “Selected Value Text” becomes the new value of the variable. This way, each radio button can assign a different value to same variable.
When a calendar control is bound to the variable, its value is set to the date selected by the control. Since variables can preset the value of visual controls and also be set by them, binding is a powerful and often-used technique.