It depends on what you are trying to do. If you want to write a command line tool, choose 'C++ Tool' from the New project dialog. If you want to build a GUI application you choose either 'Cocoa Application' or 'Carbon Application', depending on whichever framework you want to use.
The Cocoa projects assume that you are going to use Objective-C, but you can also use C++ (which Apple calls Objective-C++).
If you are wanting to make normal Mac gui type apps I would recommend that you look at using Objective-C. It is easy to learn, if you are familiar with C, simple to use, and because it is the 'natural' language for OS X development, it gives you the full power of the Cocoa frameworks. There is plenty of info that comes with XCode, including a full manual for Objective-C.
The Cocoa projects assume that you are going to use Objective-C, but you can also use C++ (which Apple calls Objective-C++).
If you are wanting to make normal Mac gui type apps I would recommend that you look at using Objective-C. It is easy to learn, if you are familiar with C, simple to use, and because it is the 'natural' language for OS X development, it gives you the full power of the Cocoa frameworks. There is plenty of info that comes with XCode, including a full manual for Objective-C.