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

please check this link :
What is the File’s Owner (in Interface builder)?
confused difference between Custom Class for an Object and for the File’s Owner and steps via IB

in first screen shot : you should set the custom class of your View .

and in the second screen shot (files owner) you can Set the file’s owner to your UIView subclass so that you can connect outlets to it