If you keep seeing the same patterns appearing no matter how close you look at something, then it’s fractal. Like mountains, which look a lot like the rocks they’re covered in. Or trees, where each branch looks like a smaller tree with lots of even smaller trees sticking out of it, and even the leaves have their own tree pattern. Or a lake-shore, where the water finds smaller and smaller gaps to flow into, right down to microscopic cracks that look like giant valley’s if you look close enough. Fractals have some interesting properties, like having somewhere between 2 and 3 dimensions, or having infinite length and zero area.