Window management on your Mac
It’s easy to find yourself with a dozen open apps and one or more windows for each app open on your desktop. Luckily, there are some efficient ways to see and navigate the windows you have open. When you want to focus, you can expand one app to fill the whole screen or choose two apps to share the screen. When you need to find a window that’s buried, use Mission Control to show all your open windows in a single layer. You can even create multiple desktops (called spaces) to view only specific windows, and then move between the spaces.
Use the whole screen. Use full-screen view when you want your app to fill the whole screen. Many apps on your Mac, such as Keynote, Numbers, and Pages, support full-screen view. In full screen, the menu bar is hidden until you move the pointer over the top of the screen, or you can choose to always show the menu bar. To enter or leave full-screen view, move the pointer over the green button in the top-left corner of the window, then choose Enter Full Screen from the menu that appears. See Use apps in full screen in the macOS User Guide.
Split the screen. Use Split View to work in two app windows side by side. Like full screen, the two windows fill the screen. Move the pointer to the green button in the top-left corner of a window you want to use, then choose Tile Window to Left of Screen or Tile Window to Right of Screen from the menu that appears. Click another window and it automatically fills the other half of the screen. When the pointer is over the green button, the menu that appears has options to switch apps, take the two windows to full screen, and more. See Use apps in Split View in the macOS User Guide.
Mission Control. Quickly move your open windows into a single layer, then click a window to return to regular view with that window in front and active. If you have additional desktops (spaces) or have apps in Split View, they appear in a row along the top of the screen. To enter or leave Mission Control, press 
on the top row of your keyboard, or press Control-Up Arrow. You can also add the Mission Control icon 
to the Dock. See See open windows and spaces in Mission Control in the macOS User Guide.
When one desktop isn’t enough. Organize your app windows into multiple desktop spaces, then switch between them as you work. To create a space, enter Mission Control and click the Add Desktop button 
. Use keyboard shortcuts and Mission Control to move between your spaces. You can drag windows from one space to another and add or delete spaces as you work. See Work in multiple spaces in the macOS User Guide.
That horizontal traffic light. The red, yellow, and green buttons in the top-left corner of every window aren’t just for show. Click the red button to close an app window. For some apps, this quits the app and closes all open windows for the app. For others, it closes the current window but leaves the app open. The yellow button closes the window temporarily and puts it in the right side of the Dock. When you want to reopen it, click it in the Dock to expand it. And the green button is a quick way to change your windows to full screen and Split View, and more.