Forms are the graphical representation of tables and their fields. Forms contain components (fields) and controls, typically including "OK" and "Cancel" buttons, and provide a high-level abstraction of standard or custom widgets. These widgets are much easier to manipulate than the GUI's underlying API.
At design time, visual controls (buttons, text boxes, etc.) and non-visual components (database connections, layout helpers, etc.) are placed on forms. These controls and components are positioned and sized interactively, and their properties and event handlers are set with a form editor.
At runtime, automatically generated code creates instances of such controls and components and sets their properties.