detailed explanation of a sherical gyroid code and how to modify the code to obtain different pores sizes and numbers

***I have the code of a spherical gyroid below which I have used to print a 3D object sphere. i will need a detailed explanation of all the terms starting from a = 3 pi till mesh. moreover i printed the 3D onject and had the below object, which parameters can i edit to have so many pore sizes. The code is given below:

a = 3 [Pi];
mesh = BoundaryDiscretizeRegion[
    ImplicitRegion[
     Sin[x] Cos[y] + Sin[y] Cos[z] + Sin[z] Cos[x] < 0 && 
      x^2 + y^2 + z^2 < a^2, {{x, -a, a}, {y, -a, a}, {z, -a, a}}], 
    MaxCellMeasure -> .1/10]; // AbsoluteTiming

mesh***