GravityCoreBlock is placed as core of star, which is auto-generated in world.
And also, you are able to craft it, and create your own star(or cylinder type space colony).
When you are to make your own, you need to know about "star type".
Type can be chanded pressing top right button of GravityCoreBlock GUI.
Here are descriptions about each type.
Generates sphere type gravity field.
When terraform, It makes sphere shape.
Generates cubic type gravity field.
No terraform for this type.
Generates cylinder type repulsive field.
When terraform, It makes cylinder shape.
So, what's Terraform?
It's a function of GravityCoreBlock helps making your own star.
First, you need to set a "star type" as I wrote above.
Second, you need to set star size(as "StarRad" in GUI, which means radius of star).
Last, place some blocks to "TerraformingMaterials" inventory.
After all is done, GravityCoreBlock starts to make a shape from y-high to y-low,
using blocks in "TerraformingMaterials" inventory.
It takes a while for small star, takes long time for bigger one.
When you need to stop function, just displace block from "TerraformingMaterials" inventory.
When you need to reset TF work, change either type or size of GravityCoreBlock.