Can anybody help me in understanding the concept of File Owner in xcode

I am unable to get the concept of File owner in xcode.

Whenever I am using a ViewContoller then i specify my viewcontoller file(say MyViewController) as the file owner in the xib. Is this because i am connecting my IBOutlets in the MyViewController to the xib? But if this is the case while creating the app in the main window why we specify UIApplication as the File owner. So i guess it may not be related to the IBOutlets concpet. Even when i am customising the UITableViewCell I am using its file owner as the NSObject andthe file where i am conectingthe IBOutlets as its type. So i ma not clear what file should i specify as the File owner for a xib? Please Help.

Thanks in advance