Control
In OpenDCL, a control is a discrete user interface element. Normally an OpenDCL control is directly analagous to a Windows control (such as a button, text box, etc.), but some controls are more complex and consist of multiple Windows controls working in unison. Note that forms are also controls in OpenDCL.
Form
A form is a template that is used at runtime to create an instance of a dialog box inside AutoCAD. OpenDCL Studio is used to create and interactively edit forms by placing controls on the form and setting design time properties of the form and its controls.