The Fibonacci Sequence is (0, 1,) 1, 2, 3, 5, 8, 13, 21, 34, 55, etc. Each number plus the previous number equals the next. Rabbits, snail shell spirals, Mandlebrot fractals... All basically follow that sequence.
The cooler part is the Golden Number - Any of those two numbers divided inversely equals 1.618 (or regularly as .618). THIS you see a lot. Architecture, art, look at your knuckles - The long section is approximately 1.618 x the length of the next section, which is 1.618 x the length of the tip section.
"Gee, John - You must've been a wiz in mathematics!"
Not at all... I hated math.
This is just a little of what the Discovery Channel has shown me.
How Tool is using it, I can't say that I know... Not that I don't like them, I just don't have any discs here to reference.