In a UI control, it is the property that determines the object it interacts with to get/set data, determine security, etc. Typically it refers to a bizobj, in which case it should be the same as the DataSource for the bizobj. But Dabo can also resolve other references, such as
self.Form.someControl, which will bind the value of the control to that object, with the DataField being the property of that object that the control's Value is bound to. You can also set DataSource to a RegID of another control, and the form will resolve that reference at runtime.
The first value in each tuple is the field name. The second value of each tuple is the dabo data type.