That is improve the status of a region on a planet.

Is it just to increase the Terraforming Funding?

And is "Natural Economic Growth", money that goes towards the installations in the regions?

From what I have read and seen you need to get specific technologies that allow this. The one I can think of off the top of my head is Sunlight Redirection. I assume from there it is just something you build in the planetary queue.

I am pretty sure that you need the tech and then "it just to increase the Terraforming Funding?"

yep, that's what the manual says: once you have researched techs that allow you to terraform, you can increase the terraforming value in the planetary view. Once you have terraformed a planet you will have to pay a constant maintenance to keep the plante at the current terraforming-level. otherwise it will slide back.

But you dont need to bother about that to much, the AI handles that (too) :)

Set 2 DEA dev plans

1:- Yellow Ring - Terraform, Terraform, Research
2:- Red Ring - Terraform, Terraform, Terraform

If the tech doesnt exist it wont terraform it at all
if it does it will kick in

Nice eh?