Recently this question was asked in interview to a candidate:
We switch back to main window or default content after switching to a new window or frame, but not in case of Alert even we are switching to it.
When we switch to a new window or frame, actually we jump to another DOM. A new window is also a DOM and a frame is also a DOM inside a DOM. This is the reason, when we switch to them using selenium methods, it returns a WebDriver. When work is done in new DOM, we need to switch back to parent window.
If you have any doubt, feel free to comment below.
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