Here is a bit of how it works~
(the highly simplified way)

BASIC
It first generates the base terrain using some basic sine+cosine functions that get averaged to create mountains.
Then it creates trees and other plants on the top layer
It then creates stone on bottom layers

UNDERGROUND
It will start by drawing some splats of dirt and then move on to ores.
The ores just draw a splat of a certain ore type. that's it.
Then we have caves…
Caves are generated using lots of splats and curved lines in order to fill an area with air, but i could go on about how they are actually made.
Then there are splats of liquid such as water/lava
finally, structures. They fill an area up with a preset structure. (the mineshaft is random*)

*it uses a preset script to generate it

if you have any more questions, i will probably answer them.

here is how the splat function works by the way:

what is the code for genorating everything and how do you make a discution?

wow is that all the code

Grid Drawing: