Recursion

In recursive definitions, we similarly define a function by defining the function of larger elements in terms of that of smaller ones. Recursion is a general term for the practice of defining an object in terms of itself (or of part of itself). There are many problems that are most easily solved by recursive programming, instead of iterative programming.

Recursion - Browse this tutorial on Recursion. Make sure you spend some time on the "Recursive Searching and Sorting" topic

Animation of Recursion - An easy to read introduction to recursion with great animations of code and data.