How to Minimize a Window on a Mac
If you don’t want to close a window but you’re not currently working on it, you can minimize it so that it doesn’t clutter up your Mac screen. When you minimize a window, your Mac places the minimized window as a tiny icon on the right side of the Dock.
A minimized window icon on the Dock actually displays the contents of that window. If you squint hard enough (or have a large enough screen), you can see what each minimized window contains.
To minimize a window, choose one of the following:
Click the Minimize button of the window you want to tuck out of the way.
Click the window you want to minimize and choose Window→Minimize (or press Command+M).
Double-click the window’s title bar.
To open a minimized window, move the mouse over the minimized window on the Dock and then click the mouse button. Your minimized window pops back on the screen.