How does this Mandelbrodt Set code work?

Taken from: http://www.mathworks.com/help/distcomp/examples/illustrating-three-approaches-to-gpu-computing-the-mandelbrot-set.html

I don't understand the significance of the count and inside variables and what function they serve for the entire code.

    maxIterations = 500;
    gridSize = 1000;
    xlim = [-0.748766713922161, -0.748766707771757];
    ylim = [ 0.123640844894862,  0.123640851045266];
    % Setup
    t = tic();
    x = linspace( xlim(1), xlim(2), gridSize );
    y = linspace( ylim(1), ylim(2), gridSize );
    [xGrid,yGrid] = meshgrid( x, y );
    z0 = xGrid + 1i*yGrid;
    count = ones( size(z0) );

    % Calculate
    z = z0;
    for n = 0:maxIterations
        z = z.*z + z0;
        inside = abs( z )<=2;
        count = count + inside;
    end
    count = log( count );

    % Show
    cpuTime = toc( t );
    fig = gcf;
    fig.Position = [200 200 600 600];
    imagesc( x, y, count );
    colormap( [jet();flipud( jet() );0 0 0] );
    axis off
    title( sprintf( '%1.2fsecs (without GPU)', cpuTime ) );

Answer 1

[dpb]

Not to give it away too easily, see <Mandelbrot>. You should understand fairly early into the explanation, but the answer is explicitly given by the end... :)