Post processors are a way that you can add optional features to your terrain generation. They are in development and are thus disabled by default, but you can enable them in the config. Here's a list:

We beat Mojang to the cave update :)

Simplex caves are large and interconnected. They are mostly finished but require some more testing before they can be added as a default.

The word "simulation" is used very loosely around here.

Takes chunks out of the land in random areas, sometimes exposing stone. It's supposed to represent areas in the world where stone comes out of the ground. NOTE: Grass sometimes spawns in the air in eroded areas, sadly this is a vanilla bug that couldn't be fixed by us (Believe me, we tried everything).

I would like to thank the 1456 blocks of TNT who valiantly sacrificed themselves for this screenshot.

Separates the world into distinct rock layers! It may make survival hard, so keep that in mind. This works well with the Erosion post processor.