What exactly is the Mandelbrot Set and what does it represent?

Answer 1

The Mandelbrot set is a set of points satisfying a particular criterion (discussed in more detail below). It doesn't "represent" anything, it's just a set of points. The colorful images you sometimes see are not just the Mandelbrot set (a point is either in the set or it isn't), but also points outside the set colored in a particular way which can be thought of as representing how long it took to decide that the point was not in the set.

The way to generate a Mandelbrot set is this:

For each point c in some region of the complex plane (a cartesian coordinate system where the X value represents the "real" part of a complex number and the Y value represents the "imaginary" part of the complex number), a mathematical operation is performed. This operation is simply to iterate the following equation:
zn+1 = zn2 + c
(where z0 = 0).

If the absolute value of zn remains bounded, the point c is in the Mandelbrot set. If, however, the value of zn goes to infinity as n goes to infinity, then the point is not in the set.

The coloring is generally based on the number of calculations (basically, the value of n) before the absolute value got larger than some cutoff (often the cutoff is 2; once the absolute value reaches 2, the z value is certain to go to infinity eventually).

The interesting thing about the Mandelbrot set is that it's not a simple shape, as you might initially expect, but a highly irregular shape. Benoit Mandelbrot, for whom the set is named, coined the term "fractal" for such complicated shapes.