Although you can add a control to a form and then bind the control to a field, it is usually more effective to use the Field Chooser. When you bind a control, you establish a link between the control and the source of data, which in this case is a field in the item.
You can use the Field Chooser to add a control and bind it to a field in a single step. Also, in many cases, the built-in control that the Field Chooser provides has special features and capabilities that cannot be duplicated by binding a field to a standard control.
For some field types, dragging the field from the Field Chooser may not use the same control that is displayed in the built-in form. To use these controls, you must add them to the form from the Toolbox, and then bind them to the field. For example, dragging the Start field from the Field Chooser results in a basic text box on the form that is bound to the Start field. However, to get a richer date selector experience for the Start field, use the Outlook Date Picker control instead.
Some entries in the Field Chooser, such as Categories, display ellipses after them. These entries correspond to actions. When you drag one of these entries in the Field Chooser to a form page, Outlook creates a button that can be clicked to open the window for the action. Two exceptions to ellipses indicating actions are the Submit and Account fields. Each of these is an action and creates a button, but there are no ellipses in the field names.