A fractal is a never-ending pattern. It is a geometrical shape where similar patterns repeat infinitly at a smaller and smaller scale. The amazing thing about fractals is that they are all around us, existing in nature.
The way to code a fractal is by simply using recursion. A recursive function is one that calls itself over and over again infinitly or until a condition is satisfied. This goes well with what a fractal essentially is, an infinitely repetitive pattern.