On Genesis themes, the structural .wrap is essentially an element which acts as a container for content. The sample and most of the themes have it set at 1140px wide and narrower at smaller sizes.
What areas have the .wrap markup by default are:
You can see this markup in the core Genesis framework at genesis/lib/init.php line 62-64
//* Maybe add support for structural wraps if ( ! current_theme_supports( 'genesis-structural-wraps' ) ) add_theme_support( 'genesis-structural-wraps', array( 'header', 'menu-primary', 'menu-secondary', 'footer-widgets', 'footer' ) );
So the code is saying if the current theme doesn’t support Genesis Structural Wraps then add the support for the elements in the array.
So if you wanted to remove the .wrap lets say from the primary menu from your own theme you would add the theme support function without the menu-primary to your functions.php file.