Base Case: The stopping point for a recursive loop; the case that keeps recursion from continuing on ad infinitum.

Droste Effect:: Named after a Dutch ad for Droste cocoa, the Droste effect happens when a smaller, identical image is hidden somewhere in a larger one. Like any good term it has a synonym: mise en abyme

Fibonacci Series: One of the most famous recursively defined sets: each number is the sum of the last two numbers combined, except for the first two numbers, which are 0 and 1. The first couple numbers in the series are 0, 1, 1, 2, 3, 5, 8, 13…

Fractal: An image or object composed of smaller copies of itself. If you have the level of definition on the image, theoretically a fractal image will repeat infinitely, growing smaller and smaller.

Iteration: An alternative to recursion, iterative loops don't reference themselves. They usually comes in the form of a for or while loop in code.

Recursion: An algorithm that calls itself to solve a problem. By calling itself over and over, it's breaking the problem down into smaller pieces until it reaches a base case it knows how to solve. Then the base case can be sent back up to the recursive steps to continue adding to it until the whole problem is solved.

Recursive function: A function that's defined in terms of itself. Every recursive function needs to have two fundamental parts:

1. A base case
2. Recursive steps that move towards the base case