TForm = class(TCustomForm)
class PASCALIMPLEMENTATION TForm : public TCustomForm
TForm represents a standard application window (form).
When you create forms in the Form designer at design time, they are implemented as descendants of TForm. Forms can represent the application's main window, or dialog boxes, or MDI children. A form can contain other objects, such as TButton, TCheckBox, and TComboBox objects.
Examples of forms include TLoginDialog and TPasswordDialog objects.