A page layout (often referred to simply as a layout) is a collection of map elements organized on a virtual page designed for map printing. Common map elements include one or more map frames (each containing an ordered set of map layers), a scale bar, a north arrow, a map title, descriptive text, and a legend. For geographic reference, you can add grids or graticules.
Once added to a layout, elements can be selected, moved, and resized on the layout to achieve the desired look and feel. This behavior can be turned off by locking an element, preventing selection, moving, or resizing interactively on the layout. Switch between locked and unlocked views by clicking the Lock button 
next to the element in the Contents pane.
Layouts can have a landscape (wide) or portrait (tall) orientation. They can be exported and used electronically and also printed. The page size varies depending on the specifications for the output. What you see on the layout is what you will get when you print or export the map to the same page size.
A page layout can also be used to author pages of a map book. If your map has multiple pages, consider using a map series.