Find a lost window
A window on a different workspace, or hidden behind another window, is easily found using the Activities overview:
Open the Activities overview. If the missing window is on the current workspace, it will be shown here in thumbnail. Simply click the thumbnail to redisplay the window, or
Click different workspaces in the workspace selector at the right-hand side of the screen to try to find your window, or
Right-click the application in the dash and its open windows will be listed. Click the window in the list to switch to it.
Using the window switcher:
Press Super+Tab to display the window switcher. Continue to hold down the Super key and press Tab to cycle through the open windows, or Shift+Tab to cycle backwards.
If an application has multiple open windows, hold down Super and press ` (or the key above Tab) to step through them.