Full screen templates its html and flash websites design of which can be stretched and fill full screen. For flash templates we use special technology that stretch website elements like menu, texts, images for all screen - fullscreen. It's allows different users see your website template correctly and comfortable for eyes. All design elements can be displayed via full screen mode. Website template in this case more useful for viewing information and navigate thru the site.
Full screen website templates use percentage dimentions - it's allows to put elements in different position and design of website will look correctly for any screen resolution. Often we use wide slideshows and galleries that automatically fit full screen and this is the best way to view images. There are no limitation like borders or fixed width. Design of such templates more comfortable for users.