Working with data frames in page layouts
In layout view, you normally work with layout graphics and text, so when you switch to layout view, the ArcMap graphic tools initially apply only to these text elements. For example, if you use the Select Elements tool 
in layout view, by default, it will only select layout graphics and text. Graphics and text stored in the data frame or in a geodatabase annotation feature class won't be selected. In addition, if you add new text or graphics in layout view, they will be added to the layout by default.
However, you can add focus to your data frame to allow you to work inside the data frame. Focusing allows you to work as if you were in data view without having to switch from layout view.
Focusing a data frame
In layout view, focusing the active data frame allows you to work with the features and elements in that data frame as though you were in data view. You can create, delete, and edit features, graphics, and text in a focused data frame.
When working in layout view with an unfocused data frame, text and graphics that you draw are added to the page layout, stored in the units of the page, and won't appear if you switch to data view.
With a focused data frame, you can make additions and modifications to your map in the context of your map layout. For example, suppose you've used the Text tool to identify an ocean in data view, but in layout view, you see that the text is too close to the edge of the data frame. To correct this, you can simply put the data frame into focus and move the piece of text while you're still in layout view rather than switching between views.
When a data frame is in focus, a thick, diagonal line border will appear around it.
Only one data frame can be in focus at a time. A data frame that is in focus will always also be the active data frame. All the commands that operate on the contents of a data frame when it is active also work when the data frame is in focus.