Get to know the desktop
At the top of the screen is the menu bar. At the bottom of the screen is the Dock. In between is what’s called the desktop.
Menu bar
The menu bar contains the Apple menu, app menus, and status menus, and the Spotlight 
, Siri 
, and Notification Center 
icons. For more information, see What’s in the menu bar?
Desktop
Your computer’s desktop takes up most of the screen; it’s where you do most of your work. You can keep files handy on the desktop and organize them at any time. To customize the desktop, see Give your desktop a custom look.
When you open an app, its windows appear over the desktop. For more information, see Manage windows on the desktop. If your desktop becomes cluttered with open windows, you can create additional desktops, called spaces, and work in multiple spaces.
Dock
Use the Dock to quickly access apps, documents, and folders. To open items from the Dock, just click them. For example, to open the Finder, click the Finder icon (the smiling face). For more information about the Finder, see See your files in the Finder.
To easily open apps that aren’t in the Dock, use Launchpad—just click the Launchpad icon 
in the Dock.