There are some things that just do not translate into existing words on Earth, so the best I can do is create a new word and then outline the conceptual ground that I want the new word to cover. A "Fence Area" is a region of space. Every galaxy has many Fence Areas. The one that is most meaningful to you is the Fence Area for Earth. As a planet with a complex web of evolving life, Earth has a fairly large Fence Area. The basic idea is that the Earth's Fence Area extends out into interstellar space until you are about half way to to other nearby worlds that have their own life forms. The process of colonization of Earth's Fence Area has been going on for many millions of years. Trust me on this one, I'll get around to explaining it.