This type calculates the Julia set of the formula lambda*Z*(1-Z). That is, the value Z[0] is initialized with the value corresponding to each pixel position, and the formula iterated. The pixel is colored according to the iteration when the sum of the squares of the real and imaginary parts exceeds 4.
Two parameters, the real and imaginary parts of lambda, are required. Try 0 and 1 to see the classical fractal "dragon". Then try 0.2 and 1 for a lot more detail to zoom in on.
It turns out that all quadratic Julia-type sets can be calculated using just the formula z^2+c (the "classic Julia"), so that this type is redundant, but we include it for reason of it's prominence in the history of fractals.