has a number of languages and explanation
There is xcode 2.0 which is a developer framework for the mac called xcode, however the link on the page is out of date, in fact mac has moved on and it is now classed as obsolute.
There is a developer tools page at apple, http://developer.apple.com/documentation/DeveloperTools/index.html
Xcode is Apple's tool suite and integrated development environment (IDE) for creating Mac OS X software. The IDE provides a powerful user interface to many industry-standard and open-source tools, including GCC, javac, jikes, and GDB. Xcode is designed to fully support the Carbon and Cocoa frameworks and Java. It contains templates for creating applications, frameworks, libraries, plug-ins, Java applications and applets, and command-line tools. Developers can use Xcode to edit and manage source code, test code performance, and perform many other common development tasks.
there is also cocoa, another language we could look at
Just not quite sure where to point him too at the moment. But the question remains webDEV or appDEV.
Now there is a page that looks at where you want to go when developing for apple, http://developer.apple.com/gettingstarted/index.html
One here is also listed different technologies for programming in apple.
Somewhere for you to start is to look at this site, it has links to resources, software you will need to have on your mac as well as reviews of books that you may need to get your hands on.