Layouts determine the overall look and position of User Interface (UI) elements of your app.
As of version 5.3, the Components panel displays components in a tree-like hierarchy as they appear in the layout. Items which are not part of the layout hierarchy are listed separately in the Services tab.
In Web Designer, you can:
Swap a layout with one from either a template or an existing app.
Revert a layout to the last time the app was saved.