You will enter the Designer window when you open a form. Designer windows help you to design your tables, lists or reports by presenting available possibilities for each selection consecutively. 

Designer windows' contents differ from one form to another but their usage is very similar.  

You can return to the Designer window whenever you like by just selecting the “Designer” from the right-click menu of the form  or F3 key.

The selections you made in the Designer window will be displayed when you open a new form of the same type. By pressing the “Default” button you can return to the default settings.