OS X El Capitan: See open windows and spaces in Mission Control
Mission Control shows all of the windows open on the desktop, arranged in a single layer so it’s easy to spot the one you need. Apps that are in full screen or Split View, and desktop spaces you created, are shown as thumbnails in the Spaces bar along the top edge of the screen.
Enter or leave Mission Control
From a trackpad: To enter, swipe up using three fingers. To leave, swipe down. You can turn off or change the trackpad gesture in Trackpad preferences.
From a keyboard: To enter or leave, press the Mission Control key or press Control-Up Arrow. You can change the keyboard shortcut in Mission Control preferences.
Show or move all open windows
Show all open windows for the current app: Press Control-Down Arrow or swipe down with three fingers. To return to the desktop, press the keys again or swipe down.
Show all open windows grouped by app: In Mission Control preferences, select “Group window by application,” then enter Mission Control.
Move open windows aside to show the desktop: Press Command-Mission Control or F11 (on a portable computer press Fn-F11). You can also spread out on the trackpad with your thumb and three fingers.
To move the windows back, press the keys again or spread in on the trackpad.
Copy or move items using Mission Control
If you have many windows or apps open and you need to copy or move items between them or to the desktop, Mission Control can make it easier.
Copy text or an image between windows: After you copy the item, enter Mission Control to show all open windows, click a window to go to it, then paste the item.
Copy a file or folder to the desktop: After you copy the item, press Command-Mission Control to move all windows aside and show the desktop, then paste the item. Press the keys again to move the windows back.
Move a file or folder to the desktop: Start dragging the item from a window, press Command-Mission Control to move all windows aside and show the desktop, then drop the item. Press the keys again to move the windows back.
You can set options and shortcuts for using Mission Control in Mission Control preferences. Choose Apple menu > System Preferences, then click Mission Control.