[Tkinter] What can the event.widget reference be used for?

[Knickers]

Widgets bound with self.root.bind_all("", lambda e: self.focus(e)) return a widget reference through e.widget such as ".!entry2" when a widget receives the focus.

I can't find anywhere how this notation can be used to identify or access the particular widget receiving the focus. I'm sure it can be done otherwise it wouldn't be useful to report this value.

How does one use ".!entry2" to access the associated widget?