I know this site well , it is really good, and Ken Perlin is a famous man, Search Perlin in internet or 3DSMax help,Terragen, etc…
Perlin Noise enable to create Pseudo-random-procedural-(Fixed) looking natural: Texture,Vegetation(Vue 2),Landscape(Terragen), and also human looking animation,etc…
NB.: Try to compile the algorithm showed on the top of the first page and you will see a nice mandelbrot fractal (Fixed font size).
Bruno