What's the difference between custom class and file's owner setting in xib file?

Question

In a custom xib file, what\'s the difference between the two following setting methods shown in the images below?

Answer 1

When you add custom UIView with XIB you init this custom view in some UIViewController and write:

let nib = UINib(nibName: "CardView", bundle: nil)
let view = nib.instantiate(withOwner: self, options: nil).first as! CardView

File's owner (in withOwner: parameter) this is usually owner is a ViewController where you add your custom UIView