What is the meaning of Active window in english?

The window in front (foreground) of all other open windows, on a graphical user interface. For example, the Internet browser window you are using to read this web page is CONSIDERED the active program or active window. The IMAGE below contains another example of an active window. The active window, labeled in red, is the text document window open above the browser window.

To activate a window, you can do any of the following.

• Click or tap the window title bar.
• Click or tap anywhere in a visible portion of the window.
• In Microsoft Windows, click or tap the icon in the Taskbar.
• In Microsoft Windows, press and hold the Alt key and while holding press the Tab key until you get to the window you want to be active.
• On the APPLE macOS, you can click the icon in the Dock.

Once active the window appears above all other windows and may HIDE any previous active window. For example, in the above picture because the inactive window is maximized if it became the active window it would hide the smaller window.