Why do some XIBs appear to be groups containing other files, and what is the purpose of those files

I think it is a very basic question.Some xib,plist look like a group((see this pic arrow on left)mainwindow.xib,icarou开发者_运维问答selexampleviewcontroller).New.xib file is normal.

what is the difference between this two?

where to use?

what is en?

How to create them?

It is used for Localization purposes. You can have different nibs based on the language. These just represent the different nibs for different languages. For example consider an app which has a button or image in one of its view, we can have another nib file for the same view for a different language to show the contents of the view in that specific language

go through these links

Link 1

Tutorial

I guess en is used for localization. It is used when you need to create application in a different language as per client requirement.