Meaning – An active window, in a computer, is the window that can receive input commands from the keyboard.
When you are using a computer, there are situations where you have multiple applications open, and each application occupies its own window on the computer screen. Now, in order to interact with a specific application or window, the first thing we do is click on it to make it active.
Once the window is active, you can interact or input commands to the same using the keyboard. It is important that you have the application you want to use, as the active window. If there is no active window, then the commands you punch in will have no effect.