Iteration and recursion are both techniques that you can use for implementing solutions in a programming language. I look at both of them as a way of thinking about a problem and solving it. The most important thing to keep in mind before we start discussing them is:

For any problem that can be solved via iteration, there is a corresponding recursive solution and vice versa.

For a programmer, it is important to understand both techniques, and be aware of their differences and when to resort to one technique in favor of the other. Let's start!