Window scope is for components specified to live in the scope of a browser window.
You can refer to ATG Component dos and donts | ATG Topics
ATG support Window scope which allows you to associate specific component instances with a specific browser window. Such components need to live longer than a request and also need to be different for every browser window associated with the user’s session.
Hope this helps
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Window scoped components are used in Commerce Service Center (CSC), its basically used to work with multiple customer profiles/orders at the same time. Its a window/tab scope, meaning in the same browser, you can open multiple tabs.
you can also refer this thread that i had created : ATG Component Scoping