You use the <mx:Binding> tag to tie the data in one object to another object. When you use the <mx:Binding> tag, you provide a source property and a destination property. You can use the <mx:Binding> tag to completely separate the view, or user interface, from the model. the <mx:Binding> tag also lets you bind different source properties to the same destination property.
MXML Syntax
The <mx:Binding> tag has the following syntax:
<mx:Binding
source="No default."
destination="No default"
/>
For example, you might bind the text property of the name field of one form to
the text property of the name field of another form, as follows:
<mx:Binding
source="billForm.name.text"
destination="shipform.name.text"
/>