In this hour, you have seen the messaging structure that is at the heart of Objective-C. It is not just another way of talking about the calling of methods that other languages use; it is a different way of constructing software. You see in later hours how the messaging architecture helps to implement dynamic aspects of Objective-C programs.
The common alloc and init methods have been used in this hour as examples. You have also seen how you can work with them and construct a hierarchy of designated and secondary initializers to construct your runtime objects.