Samsung have Multi Window functionality and underappreciated feature. With this function turned on, you can run two apps on the screen simultaneously, giving you serious multitaking power.You can drag one window to another.
To get started, make sure Multi Window is turned on in the QUICK SETTINGS MENU. Then swipe the tab from the left edge of the screen to the right. Now drag app icons from the tray that appears in the top and bottom windows as your compatible. Now you can attach a photo to an outgoing email just by dropping it, or browse the Web while you can check your messages.