In fractal geometry recursion refers to a loop in which the output of one stage becomes the input for the next. The Koch Curve is an early example of this type of recursion. The curve is begun by drawing a line segment and dividing it into thirds. An equilateral triangle is formed on the central segment and then the bottom of the triangle removed. This is the seed shape or generator. It is the output that now becomes the input. The visual of the Koch Curve will help the explanation.
Here is iteration applied to my art.