If you can read the Apple documentation , you can find the answer. Like par doc this border, plain and Done defines the style of the element .

Normal (UIBarButtonItemStylePlain)
Lights up when pressed. The default item style.
Border (UIBarButtonItemStyleBordered)
Simple style buttons with frame.
Done (UIBarButtonItemStyleDone)
The style for the button made is, for example, a button that completes a task and returns to its previous form.
For testing, you can create a demo project in Xcode and set a different style, and you can understand the difference.
Nitin gohel
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