MainWindow_iPhone.xib and MainWindow_iPad.xib contain the interface for your application. Double click to open in the interface builder.
ApName-Info.plist is the info property list which contains a list of the key-value pairs. These values specify things like the icon to display on the home screen, if the app needs a persistant WiFi connection, default language etc.
Header files. Variables, methods etc declared in these.
Pre compiled header file. This is the global header file that is added to all project files. Use to add any global imports etc.
A xib file is compiled into a nib file which is what is actually run.
The directory containing the executable and any resources the executable uses which is the output of the building the application.
#import (#include) and @class
In Objective-C #import is the same as standard C #include except that the file is only ever included once.
If you don’t want to import the header file for a class but want the compiler to know the class exists use ‘@class’ instead (much faster when compiling large projects):