Grid layout : This is the default. Controls are placed exactly where you draw them and they have absolute positions on the page. Use grid layout for Windows-style applications, in which controls are not mixed with large amounts of text.
Flow layout : This places controls relative to other elements on the page. If you add elements at run time, the controls that occur after the new element move down. Use flow layout for document-style applications, in which text and controls are intermingled.